UGENYA / UGUNJA DISTRICT JOINT EVALUATION TEST,...

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UGENYA / UGUNJA DISTRICT JOINT EVALUATION TEST, 2013

Kenya Certificate of Secondary Education (K.C.S.E)

233/1

CHEMISTRY

PAPER 1

July/August, 2013

Time: 2 hours 1. The flame produced from the Bunsen Burner when the air-hole is fully open is strong and produces little

or no soot. Explain. (2 marks)

2. In the chemical equation below identify the acid and give a reason for your choice.

C2H5O-(aq) + H2O(l) C2H5OH(aq) + OH-

(aq) 3. Below is information above about four metals A, B, C and D (not actual symbols). Metal C does not react with

cold water but reacts with steam. D does not react with steam but reacts with dilute acids. B reacts with cold

water while A does not react with dilute acids. Arrange the metals in order of reactivity starting with the

least reactive. (2 marks)

4. Study the sequence below and answer the questions that follow.

a) Write the chemical equation for the reaction in step 1. (1 mark)

b) Name the method used to obtain nitrogen from air. (1 mark)

c) State one observation that would he made in step 3 if copper (II) oxide was used-instead of lead (II) oxide.

(l mark)

5. Study the reaction scheme below.

i) Write a chemical equation for the reaction leading to formation of the colourless solution. (l mark)

ii) Name the compound that is the colourless solution.

iii) Write an equation for the reaction between the metal chloride and sodium carbonate. (l mark)

6. a) Write the structural formula of

i) 3, 3 - dimethylpent - I - ene. (l mark)

ii) 4 - bromo - 2 - methylpentan - 2 - ol (l mark)

7. Name the major ores from which the following metals are extracted.

a) Sodium .................................................................................................................................... (l mark)

b) Lead ............................................................................................................................................................................. (1 mark)

c) Iron .................................................................................................................................................................. (1 mark) 8. a) State Graham's law of diffusion. (l mark)

b) The diffusion of molecules of ammonia and an unknown gas B through air was investigated. The distance covered by

the two gases is shown by the apparatus below

A white ring indicated after 4 minutes.

Calculate molar mass of B (N =14, H = 1) (2 marks)

9. 6.8g of Aluminium sulphate were dissolved in 200cm3 of water, Calculate the molar concentration of the sulphate ions in

the solution (Relative formula mass of aluminium sulphate is 342). (3 marks)

10. Study the following and answer the questions below.

2

Cr2O42-

(aq) + 14H(aq) + 6e- 2Cr3-(aq) + 7H2O(l)

By using change in the oxidation state of chromium, explain whether chromium is oxidised or reduced. (2 marks)

11. An acid base indicator is a substance with specific colour for both acidic and alkaline medium. A particular

indicator used in science laboratory attains the following equilibrium state.

XOH X(aq) + OH-(aq)

(Blue) (Red)

State and explain the colour of this indicator when added to

a) Slaked lime (1½ marks)

b) Lemon juice (1½ marks)

12. Using dots (•) and crosses (x) to represent electrons show bonding in

a) Ethyne molecule (C = 6, H = 1)

b) Hydroxonium ion H3O 13. Water gas is a mixture or carbon (II) oxide and hydrogen gas while producer gas is a mixture of carbon (Il) oxide and

nitrogen gas. Using equations, explain why water gas is a better industrial fuel than the producer gas. (3 marks)

14. During the working of a lead-acid accumulator the two main reactions taking place are

Pb(s) Pb2(aq) + 2-

PbO2(s) + 4H(aq) + 2- Pb2+(aq) + 2H2O(l)

a) Write the cell representation of this cell. (1 mark)

b) Explain one disadvantage of dilute Sulphuric (VI) acid as the electrolyte. (2 marks)

15. a) Define a hydrogen bond (1 mark)

b) Water (H2O) is a liquid at room temperature while hydrogen sulphide (H2S) is a gas at room temperature.

Explain. (2 marks)

16. When wet red coloured flower petals are dropped in a gas jar full of sulphur (IV) oxide gas they get discoloured. When

wet red and blue litmus paper are placed in a gas jar full of chlorine gas they are also discoloured (bleached). Using

relevant equations only, explain the difference in the two modes or bleaching. (3 marks)

17. Study the diagram below and answer the questions that follow.

I. Write half equations for production of gases. (1 mark)

II. Electrolysis of dilute sulphuric (VI) acid can be referred to as electrolysis of water. Explain. (1 mark)

III. The bulb does not light when dry HCl(g) is used without water. Explain. (1 mark)

18. a) Name any two reagents for the laboratory preparation of hydrogen. (1 mark)

b) Describe the chemical test for hydrogen gas. (2 marks)

19. Describe how solid sample of sodium sulphate can he prepared starting with 100cm3 of 1 M sodium hydroxide

solution. (3 marks)

20. Use the information in the energy cycle diagram below to answer the questions that follow.

i) What is the name given to the energy changes H1, H2, H3? (1½ marks)

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ii) Given that lattice energy or magnesium chloride -2493kJ I mole, hydration energy of magnesium

ion=189kJ/mole while hydration energy of chloride ion is -384kJ I mole. Calculate the enthalpy of solution

of magnesium chloride. (1½ marks)

21. a) Draw a well labelled diagram to show how iron sheets are galvanised. (2 marks)

b) Briefly explain why stainless steel is preferred to mild steel for making cutlery and sinks. (1 mark)

22. The table below gives-some information about certain chemical substances. The letters used are not the actual

chemicals symbols or formulae.

Substance Melting point oC Boiling point oC Electrical conductivity

Of solid Of liquid In water

A

B

C

D

E

F

1540

-114

712

-39

2045

1700

3000

-85

1418

357

3000

2776

Good

Poor

Poor

Poor

Poor

Poor

Good

Poor

Good

Good

Good

Poor

Insoluble

Good

Good

Insoluble

Insoluble

Insoluble

From the table, select

i) Two substances that cannot be e1ements. (1 mark)

ii) A substance that is likely to have giant atomic structure. (l mark)

iii) A substance that is likely to consist of molecules and which produce ions when added to water. (1 mark)

23. State and explain what happens to red and blue litmus paper used in a gas jar full or dry ammonia. (1 mark)

b) Using Lead (II) nitrate explain how the presence of chloride ions can be tested. (2 marks)

24. Briefly explain the following observations.

a) Atomic and ionic radius decrease as one moves across the period from left to right. (1 mark)

b) The ionic radii of a gas e.g chlorine is bigger than its atomic radius. (1 mark)

25. a) Define the term solubility as used in chemistry. (1 mark)

b) Salt Q has a solubility of 30g / 100g of water. 55g of salt Q is stirred in 65g of a solution which contains 10g

of salt Q. How much more of salt Q will dissolve in the solution? (3 marks)

26. One of the pollutants from the car exhaust fames is nitrogen (IV) oxide. Explain how it is produced from the

internal combustion engine. (2 marks)



233/2

CHEMISTRY

PAPER 2

TIME: 2 HOURS

1. a) The table below shows the atomic numbers of elements in the periodic table represented by the letter A to I.

The letters are not the actual symbols of the elements.

Element A B C D E F G H I

Atomic number 3 7 8 9 11 12 13 14 16

I. Select two divalent elements that would form ions with electronic configuration of 2.8. (l mark)

II. Select two elements in the same group. (1 mark)

III. Select the non-metal and the metal that would react most vigorously with each other. (1 mark)

b) i) Draw cross (X) and dot (•) diagram for the compound formed between hydrogen and element B. (2 marks)

ii) The compound formed in b(i) above does not conduct electric current in gaseous form but do conduct in

aqueous form. Explain. (2 marks)

c) Compare the melting points of oxides of H and I. Explain your answer. (2 marks)

d) Write an equation for the reaction that takes place between elements G and C. (1 mark)

c) Describe how solid mixture of the sulphate of element E can be separated from lead (II) sulphate. (3 marks)

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2. The now chart below outlines some of the processes involved in extraction of copper from copper pyrites.

Study it and answer the questions that follow.

i) Name the ore from which copper is extracted. (1 mark)

ii) Write an equation for the reaction in the 1st roasting chamber. (1 mark)

iii) Name gas K. (1 mark)

iv) Give the name and the formula of slag M. (2 marks)

v) Name the impure copper X. (1 mark)

b) i) Pure copper is obtained from impure copper by electrolysis. Name the material used at anode and

cathode and the electrolyte. (3 marks)

ii) Write equations for the reaction at: Anode (I mark) Cathode .............................................................. (1 mark)

iii) State two uses of copper metal. (l mark)

3. In an experiment to determine the heat of displacement of copper by calcium. 0.25g of calcium powder was

added to excess 25.0cm3 of 2.0M copper (II) nitrate solution. The temperature of the mixture was taken after

everyone minute for ten minutes and the data obtained is shown below.

Time mins 0 1 2 3 4 5 6 7 8 9 10

Temp oC 25.0 27.0 28.7 31.0 33.3 35.0 35.0 35.0 33.4 31.7 30.0

i) Draw a graph of temperature against time (mins). (3 marks)

ii) From your graph determine the highest temperature attained. (1 mark)

iii) Calculate the heat change during the reaction.

(Specific heat capacity of solution = 4.2 Jg-1K-1, Density of solution = l g/cm 3) (2 marks)

iv) Determine the molar heat of this displacement reaction. (Ca = 40) (1 mark)

v) Write the thermochemical equation for the reaction. (1 mark)

b) The energy-level diagram for uncatalysed decomposition of hydrogen peroxide is as shown.

i) On the same axes sketch a graph that would be obtained if a spatula-endful of manganese (IV) oxide were added

onto the hydrogen peroxide. (1 mark)

ii) Indicate on the sketch graph:

a) Activation energy.

b) Enthalpy change during the chemical decomposition.

4. a) Describe the chemical tests that can be used to distinguish between the following compounds.

H4H10O and C3H6O2 (2 marks)

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b) Study reaction scheme below and answer the questions that follow.

i) State the name and draw the structural formulae of the following compounds. (3 marks)

ii) Write a chemical equation leading to formation of gas P. (l mark)

iii) State the reagents and conditions necessary for step I. (1 mark)

iv) Name compound B. (1 mark)

c) 20cm3 of 2M of a solution of B required 40cm3 of solution A. Calculate molarity of solution A. (3 marks)

5. A piece of marble (calcium carbonate) is put into a beaker containing an excess of dilute hydrochloric acid which

is placed on a reading balance. The mass of the beaker and its contents is recorded every 2 minutes as shown in

the table.

Time 0 2 4 6 8 10 12

Mass (g) 126.44 126.31 126.19 126.09 126.03 126.00 126.00

a) i) Why is there a continuous loss in mass of the reaction mixture? (1 mark)

ii) State and explain one way in which the experiment can be made more rapid. (2 marks)

iii) Give a reason why the mass remains constant after 10 mins. (1 mark)

iv) Write the name and formula of each of the two remaining ions after the reaction. (2 marks)

v) The solution remaining was evaporated to dryness and the mass of the beaker and the remaining solid was

97.63g. The following day the mass was 98.63g. Explain what caused this change in mass. (2 marks)

6. a) A student set up an experiment for the electrolysis of CuSO4(aq). A current of 0.5A was passed through the

circuit for 3860 secs. A mass of 0.64g of copper was deposited (Cu=64.0).

i) Which electrode gained mass? (1 mark)

ii) How many coulombs are needed to deposit one mole of copper? (2 marks)

b) Use the data below to answer the questions that follow.

i) Define the standard electrode potential. (2 marks)

ii) From the above list select giving a reason:

a) Most powerful oxidizing agent, (1 mark)

b) Most powerful reducing agent. (1 mark)

iii) Which two half cells when combined would give the largest e.m.f? (1 mark)

iv) Work out the emf of the cell in (iii) above. (1 mark)

v) Write down the cell notation representation for the cell in (iii) above.

vi) Draw a well labeled diagram for the cell in (III) above indicating the direction of the electron flow by use of

an arrow on the diagram. (2 marks)

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7. Use the following scheme to answer the questions that follow.

a) Name the raw materials A and B (2 marks)

b) Write equation for reaction taking place at Q and T

(2 marks)

c) Name recycled substances. (1 mark)

d) Name process S and K (2 marks)

e) Name by-product E

(1 mark)

f) Give two uses of baffles found inside the Solvay

towers. (2 marks)

g) Give two commercial uses of sodium carbonate.

(2 marks)



233/3 CHEMISTRY PAPER 3

July / August, 2013

1. You are provided with;

- 5g of potassium chlorate - Distilled water in wash bottle

You are required to determine the effect of concentration on the solubility of the salt.

Procedure

Transfer 5g of potassium chlorate into a clean dry boiling tube.

Run from a burette l0cm3 of water into the boiling tube.

Warm the mixture till all the solid has dissolved. Place a thermometer in the solution and cool under the tap water

stirring gently with the thermometer.

Note and record the temperature at which crystals start to appear. Run another 5cm3 of water from the burette to

the solution and repeat the procedure to note the temperature at which crystals start forming again. Continue

adding 5cm3 portions of water until 35cm3 of water have been added and noting the temperature at which crystals

start to form. Record the results in the table below.

a)

Total volume of water added to 5g KClO3 10 15 20 25 30 35

Crystallization temperature

Mass of KClO3 in grams per 100g of water

b) Calculate the values of mass of KClO3, in grams per l00g of water and record your values in the table above.

(3 marks)

c) From the table of results plot a solubility curve. (3 marks)

d) From the graph determine:

i) The solubility in g of KClO3 in 100g of water at 25°C. (l mark)

ii) The temperature when the solution will contain 22g of KClO3 (l mark)

e) From your results calculate the mass of KClO3 that will crystallize out when a hot solution of 52°C is cooled to

37°C. (l mark)

2. You are provided with:

- Acidified potassium manganate (VII), solution U - Oxalic acid, solution W

You are required to determine how the rate of reaction of potassium manganate (VII) with oxalic acid varies with

changes in temperature.

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Procedure

Using a measuring cylinder, place 10.0cm3 portions of solution U into 5 separate test tubes in a test tube rack.

Clean the measuring cylinder and use it to place 10.00cm3 of solution W into a boiling tube.

Prepare a water-bath by placing 100cm3 of water in beaker and start heating it. Insert a thermometer in solution W in

the boiling tube and place the boiling tube in hot water-bath till the solution W attain a temperature or 40°C. Remove

the boiling tube from the water bath and place it in a test tube rack and add the first portion or solution U. Shake and at

the same time start a stop watch. Record the time taken for the purple colour of the mixture to be decolourised in the

table below.

Repeat the experiment by using 10.0cm3 portions of solution W at temperatures of 50°C, 60°C, 70°C and 80°C

Record the time taken in the table below. Complete the table by computing 1/ time (Sec-1)

a) (5 marks)

Temperature of solution W (oC) 40 oC 50 oC 60 oC 70 oC 80 oC

Time taken for the mixture to decolourise (t) sec

Reciprocal of time 1/ time (Sec-1)

b) Plot a graph of 1/ time (Sec-1) against temperature. (3 marks)

c) From the graph, determine the time taken for decolourisation of the mixture, if the temperature of solution

W was 65°C. (1 mark)

d) How does the rate of reaction of potassium manganate (VII) with oxalic acid vary with temperature? (1 mark)

3. a) You are provided with solid Q.

You are required to carry out the tests below to determine the identity of Q.

i) Put all the solid Q in a boiling tube and add 12cm3 of distilled water and shake thoroughly. Divide the

resulting solution into six portions.

Observations Inferences

(1 mark) (1 mark)

ii) To the first portion add aqueous sodium hydroxide until in excess.


(1 mark) (1 mark)

iii) Insert a glass rod to the second portion and burn it in a non-luminous flame.


(1 mark) (1 mark)

iv) To the third portion add 3 drops of lead (II) nitrate solution


(1 mark) (1 mark)

v) To the fourth portion add about l cm3 of acidified potassium manganate (VII)


(1 mark) (1 mark)

vi) To the fifth portion add about 1 cm3 of acidified potassium dichromate (VI)


(1 mark) (1 mark)

vii) Give the identity of Q. (1 mark)

b) You are provided with liquid M. Carry out the tests below and record your observations and inferences in the

spaces provided.

i) Place 3 drops of liquid M on a watch glass. Ignite the liquid using a Bunsen burner.


(½ mark) (½ mark)

ii) To about 1 cm3 of liquid M in a test-tube add about 1 cm3 of distilled water and shake well.


(½ mark) (½ mark)

iii) To about cm3 or liquid M in a test-tube, add a small amount of solid hydrogen carbonate.


(1 mark) (½ mark)

iv) To about l cm3 of liquid M put the blue and red litmus papers.


(1 mark) (½ mark)

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KAKAMEGA COUNTY JOINT EVALUATION EXAM


233 /1

CHEMISTRY

Paper 1

1. (a) What is meant by allotropy? (1mark)

(b) Identify the two crystalline allotrope’s of carbon. (1mark)

(c) Give one use of carbon black. (1mark)

2. When hydrated sample of iron (II) sulphate FeS04.nH2O was heated until there was no further change in mass,

the following data was recorded

Mass of evaporating dish = 78.94 g

Mass of evaporating dish + hydrated salt = 84.14 g

Mass of evaporating dish + residue = 81.78 g

Determine the empirical formula of the hydrated salt. (Relative Formula Mass of FeSO4 = 152, H2O = 18)

(3marks)

3. Equal volumes of 2M monobasic acids Rand S were each reacted with excess magnesium ribbon. The table

below shows the volume of the gas produced after one minute

Acid Volume of gas (cm3)

R 80

S 30

(a) Write the ionic equation for the reaction which took place. (1 mark)

(b) Explain the difference in the volumes of the gas produced. (2marks)

3. The graph below shows the changes which take place when a solid is heated.

(a) What happens to the molecules between W and X? (1mark)

(b) What is the significance of the temperatures T1 and T2? (1mark)

(c) Explain why the temperature does not rise between X and Y. (1mark)

5. In an experiment to determine the solubility of potassium nitrate at 30°C, a saturated solution was heated in an

evaporating dish until there was no further change in mass. The following data was obtained.

Mass of dish + solution = 128.9 g

Mass of dish + dry salt = 103 .9g

Mass of empty dish = 94.3 g

Determine the solubility of potassium nitrate at 30°C. (3marks)

6. The diagram below shows a setup that was used to prepare and collect a sample of nitric acid.

Sink

Cold water

Nitric acid

Potassium nitrate

Conc. sulphuric acid

Heat

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(a) Give a reason why it is possible to separate nitric acid from sulphuric acid in the setup. (1mark)

(b) Name another substance that can be used instead of potassium nitrate. (1mark)

7. Starting with lead oxide, nitric acid, sodium sulphate, water and all necessary apparatus, describe how you would prepare a

dry sample of lead (II) sulphate. (3marks)

8. Study the flowchart below and answer the questions that follow

(a) Name the reagent Z and Y

(b) Write the formula of the complex ions presented in the deep blue solution. (1mark)

9. Methane burns in air according to the equation below

CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ; ∆H = -890kJmol-1

Calculate the volume of methane which would produce 111.25kJ when burnt. (Molar gas volume = 24.0dm3) (3marks)

10. NO2 and N2O4 gases exist in equilibrium at 200C as shown in the equation below;

2 NO2(g) N204(g) ∆H = -ve

Brown Pale yellow

State and explain the observation that would be made when;

(a) A syringe containing the mixture at 200C is heated to 400C. (1mark)

(b) The gaseous mixture in a syringe is compressed. (1mark)

11. The diagram below shows a Bunsen burner when in use

(a) Name the regions labelled B and C. (1mark)

(b) What is the function of the part labelled A? (1mark)

12. A certain mass of marble chips reacted with excess dilute hydrochloric acid at 25°C. The volume of carbon (IV)

oxide gas liberated was measured after 30 seconds. The results were presented as shown in the graph below.

a) Name one piece of apparatus that may have been used to measure the volume of the gas liberated. (1mark)

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b) On the same axis sketch the curve that would be obtained if the experiment was repeated using calcium

carbonate powder . (1mark)

13. When hydrogen sulphide gas was bubbled into an aqueous solution of iron (III) chloride, a yellow precipitate

was deposited.

(a) State another observation that would be made. (1mark)

(b) Write an equation of the reaction that took place. (1mark)

14. The table below shows the atomic numbers of elements P, Q and R.

(a) Explain why P and R would not be expected to form a compound. (1mark)

(b) Write an equation to show the effect of heat on the carbonate of R. (1mark)

15. The diagram below shows the setup that was used to prepare and collect Sulphur (IV) oxide gas.

(a) Identify the solid P (1mark)

(b) (i) Why is it possible to collect Sulphur (IV) oxide as shown? (1mark)

(ii) What happened to the red flower? (1mark)

16. (a) State Charles' Law. (1mark)

(b) The volume of a sample of nitrogen gas at a temperature of 298 K and 600 mmHg pressure was

4.8 x 1O-2m3. Calculate the temperature at which the volume of the gas would be 3.2 x 10-2 if pressure

remains the same. (2marks)

17. Element T consists of two isotopes 62T and 64T in the ratio 7: 3 respectively. Calculate the relative atomic mass of

element T. (3marks)

18. Name the process which takes place when:

(a) Solid carbon (IV) oxide changes directly into gas. (1mark)

(b) Butanol reacts with hexanoic acid in the presence of sulphuric acid. (1mark)

19. Study the standard electrode potentials for the half-cells given below and answer the questions that follow.

(The letters do not represent the actual symbols of the elements)

Eθ Volts N+

(aq) + e- N (S) ; -2.92

J+(aq) + e- J(S); +0.52

K+(aq) + e- ½ K(g) ; 0.00

½ G2(g) + e- G-(aq) ; +1.36

M2+(aq) + 2e- M(S) ; -0.44

(i) Which two half-cells would produce the highest potential difference when combined?

(ii) In the space below draw a complete electrochemical cell of the two-half cells mentioned in (i) above (2marks)

20. Study the table below and answer the questions that follow

Bond type bond energy kJmol-l

C - C 346

C = C 610

C - H 413

C - Br 280

Br-Br 193

(a) Calculate the enthalpy of the following reaction (2marks)

C2H4(g) + Br2(g) C2H4Br2(g)

(b) Name the type of reaction that took place in (a) above (1mark)

21. Briefly explain how you would obtain pure sample of lead (II) chloride from a mixture of lead (II) chloride and silver

chloride. (2marks)

Moist red flower Solid P

Heat

Hydrochloric acid

11

22. Explain the following observations; very little carbon (IV) oxide is evolved when lead carbonate reacts with dilute

hydrochloric acid. (2marks)

23. The table below gives some properties of compounds P, Q , R and S

Compound B.P. (0C) M·P.( 0C) Conductivity in water

P 77 -23 Does not conduct

Q 74 -19 Does not conduct

R -161 -85 Conducts

S 2407 714 Conducts

(a) Which one of the compounds in the table is ionic? Explain. (1mark)

(b) Give the compound that is liquid at room temperature. (1mark)

24. When a hydrocarbon fuel bums, one of the main products is acidic gas R.

(i) Identify gas R. (1mark)

(ii) What two effects does gas R have when its concentration in the atmosphere exceeds its acceptable levels? (1mark).

25. When butan - 1 – ol is oxidized by acidic potassium dichromate, a weak organic acid is formed.

Draw and name the structure formula of the acid obtained from the above reaction. (2marks)

26. Air was passed through several reagents as shown in the flow chart below.

Air

Concentrated potassium Excess hot copper Excess heated

hydroxide solution turnings magnesium powder

(a) Write an equation for the, reaction that took place in the chamber with the magnesium powder. (lmark)

(b) Name one gas that escapes from the chamber containing magnesium powder. Give a reason for your answer. (1mark)

27. When a current of6.42 A was passed through an electrolyte Y2+ ions for 10 minutes, 2.74 of Y were deposited

(i) Calculate the quantity of electricity passed in the experiment (1mark)

(ii) Determine the relative atomic; mass of Y (1 Faraday = 96000 coulombs (2marks)

28. Explain why aluminum metal is not extracted from aluminium chloride. (2marks)

29. Part of the structure of a polymer is given below.

(i) Identify the polymer. (1mark)

(ii) State one disadvantage of continued use of this polymer. (1mark)

30. The table below gives the rate of decay for a radioactive element M;

Number of days Mass (g)

0 12.8

280 0.8

Determine the half - life of the radioactive element M. (2marks)

31. Study the flow chart below and answer the questions that follow;

(a) Write an equation for the reaction between gas X and ammonia. (1mark)

(b) Write the formulae of the substance present in the mixture Y(aq) (2marks)

32. When the air-hole is fully opened, the Bunsen burner produces a non-luminous flame. Explain. (1mark)

Escaping gases

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233 /2

CHEMISTRY

Paper 2

1. (a) Clean iron filings were weighed and then placed on a watch glass containing water as shown in the

following diagram.

(i) State the observation made on the iron filings after three days. (1mark)

(ii) With a reason compare the mass of the iron filings at the start of the experiment with that of the product

after three days. (2marks)

(iii) Give the general chemical formula of the product formed in this experiment. (1mark)

(iv) An ore is suspected to contain iron metal, describe how the presence of iron in the ore could be confirmed.

(3marks)

(b) (i) Name one ore from which iron is extracted. (l mark)

(ii) What is the name of the process used in the extraction of iron metal in the blast furnace. (lmark)

(iii) The following diagram represents the blast furnace in which extraction of iron is carried out,

(i) Identify one other raw material used apart from the iron ore. (lmark)

(ii) Write the equations that lead to the formation of substance A in the blast furnace. (lmark)

(iii) State one property of the iron produced on the blast furnace. (1mark)

2. The following diagram represents the frasch pump used in the extractions of sulphur.


(i) Identify substance c and state it's purpose in this extraction process. (2marks)

(ii) The sulphur obtained in this process solidifies at 1130C. Name the allotropic form of sulphur that forms.

(1mark)

(b) The following diagram represents an incomplete set-up of the laboratory preparation and collection of dry

sulphur (IV) oxide. Study it and answer the questions that follow.

Dil. Hydrochloric acid

(i) Complete the set-up to show how a dry sample of sulphur (IV) oxide gas may be collected . (2marks)

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(ii) Describe a chemical test for sulphur (IV) oxide gas: (2marks)

(iii) Write an equation for the reaction that occurs. (1mark)

(iv) Calculate the volume of sulphur (IV) oxide produced if 315g of sodium sulphate completely reacts with

excess dilute hydrochloric acid at room temperature

(Na = 23, S = 32, O = 16 molar gas volume at room temperature and pressure = 24dm3 (2marks)

(c) Sulphur (IV) oxide can be converted to sulphur (VI) oxide as shown in the following equation.

2 SO2 (g) + O2 (g) SO3(g) ∆H = -192 kJ

(i) What is the molar enthalpy of formation of sulphur (VI) oxide? (lmark)

(ii) State the catalyst used in this reaction. (1mark)

(iii) State and explain the effect of increasing temperature on the yields of sulphur (VI) oxide. (2marks)

3. a) (i) The nucleus of a neutral atom is positively charged. Explain (1mark)

(ii) Complete the following table to show the atomic properties of elements P, Q, R and S.

(The letters used are not the actual symbols of the elements) (2marks)

Element No. of protons No of neutrons Mass number

P 1 1

Q 7 14

R 6 6

S 12 23

b) The following table shows the electron arrangement of ions of elements T, U, V and W

Ion Electron Arrangement of Ions

T+2 2,8

U- 2,8,8

V+ 2,8,8

W+2 +2222 2,8,8

(i) Which two elements have similar chemical properties? Explain (2marks)

(ii) Give the electron arrangement of element U. (1mark)

(iii) Write an equation for the reaction between elements N and U. (1mark)

(iv) With a reason, compare the atomic radius of elements V and W (2marks)

(v) To which period does element K belong? (1mark)

(vi) With a reason, compare the ionic and atomic radii of U (2marks)

4. (a) (i) State two features of members in the same homologous series (2marks)

(ii) Give the systematic names of the following compounds. (2marks)

(b) The following diagram shows the set-up used during the preparation of ethane gas in the laboratory .

(i) Name apparatus Q (lmark)

(ii) Identify substance T and S (2marks)

(iii) From the method of collection, state one property of ethane gas. (2marks)

(iv) Ethane bums in air to form carbon (IV) oxide and water.

I) Write an equation for the combustion of ethane in air. (1mark)

II) Calculate the mass in gramms of carbon (IV) oxide formed if 1.5 g of ethane were completely burnt in

oxygen. (H = 1, C = 12, 0 = 16) (2marks)

5. a) (i) What is a neutralization reaction? (1mark)

(ii) Define standard enthalpy of neutralization (1mark)

b) A student carried out an experiment to determine the standard enthalpy of neutralization for the reaction

14

between ethanedioic acid and sodium hydroxide. In the experiment 5cm3 particles of sodium hydroxide

were added to 20cm3 of ethanedioic acid and the temperature after every addition was recorded. The

following table gives a summary of the results obtained. Use the results to answer the questions that follow

Total volume of 1M NaOH added (cm3) 0 5 10 15 20 25 30 35

Volume of 0.5M ethandioic acid (cm3) 20 25 30 35 40 45 50 55

Temperature (0C) 20.0 22.0 23.0 24.0 25.0 25.0 24.0 23.0

(i) On the grid provided, plot a graph of temperature (y-axis) against the value of 1M sodium hydroxide

added. (4marks)

(ii) From the graph, determine

I) The volume of sodium hydroxide required to completely neutralize 20.0cm3 of 0.5M ethanedioic acid.(lmark)

II) The highest temperature change, ∆T. (lmark)

III) Calculate the enthalpy change for this reaction, (density of solution is 1 gcm-3 and specific heat capacity of

solution is 4.2kJ -1K-1) (2marks)

IV) Determine the standard enthalpy of neutralization per mole of ethanedioic acid

V) Draw an energy level diagram for the neutralization reaction (lmark)

6. The following flow chart shows three possible routes X, Y and Z by which copper (ii) sulphate could be made from

different starting materials by adding dilute sulphuric acid solution.

Copper (II) X Copper (II) Y Copper (II)

Oxide Sulphate Hydroxide

Z

Copper (II)

Carbonate

The following table gives some information about the solubility in water of a number of compounds of copper,

sodium and Lead.

Metal Oxide Hydroxide Carbonates Sulphate Chloride Nitrate

Copper X X X

Sodium

Lead X X X X X

Key : = Soluble X = Insoluble

Use the above information in answering the questions that follow

(a) Write an ionic equation for the reaction that occurs in route Z (1mark)

(b) In an attempt to prepare pure crystals of copper (II) sulphate by route X, excess copper (II) oxide was added to a

limited quantity of dilute sulphuric acid and the mixture warmed.

(i) Why was excess copper (II) oxide used? (1mark)

(ii) Draw a diagram to show how excess copper (II) oxide may be removed. (2marks)

(iii) Having removed the excess copper (II) oxide, describe how you would obtain pure hydrated crystal of

copper (II) sulphate. (3marks)

(c) Starting with solid sodium carbonate, copper (II) oxide, nitric acid and water, describe how copper (II) carbonate

could be prepared in the laboratory. All necessary apparatus are provided. (3marks)

7. a) Chlorine gas was bubbled through a solution of potassium oxide as shown in the following diagram.

(i) State one observation made in the test tube at the end of the reaction. (1mark)

(ii) Write an equation for the reaction that takes place. (2marks)

(iii) Using oxidation numbers state and explain which species is reduced. (2marks)

b) The following table gives the standard electrode potentials (E) for certain half-cell. Study it and answer the

question that follows.

15

Half - cell Eθ Volts

Zn2(g) + 2e Zn (s) - 0.76

Fe2++ 2e Fe(s) -0.44

I2 + 2e 2 I- +0.54

Fe3++ 3e Fe (s) +0.77

(i) From the above table, identify the strongest reducing agent. Give a reason for your answer. (2marks)

(ii) (I) Draw a diagram for the cell formed by combining the half-cells of zinc and iron. (2marks)

(II) Calculate the e.m.f of the cell in (ii) I) above. (1mark)


233 /3 CHEMISTRY PAPER 3

1. You are provided with solutions M and N.

Solution M is acidified Potassium Manganate (VII), solution N was prepared by dissolving 5.9g of solid N in

distilled water to make 250cm3 of solution.

You are required to determine the number of moles of N that react with one mole of potassium manganate

(VII)

PROCEDURE 1

Place solution M in a burette. Using a pipette filler, transfer 25cm3 of solution N into a 250cm3 conical flask.

Titrate solution N with solution M until a permanent pink colour just appears.

Record your results in table1 below. Repeat the above procedure two more times.

(a) Table 1

I II III

Final burette reading

Initial burette reading

Volume of solution M used

(b) Calculate the average volume of solution M used (1mark)

(c) Given that the concentration of solution M is 0.02M, calculate the number of moles of potassium

manganate (V II) used (1mark)

(d) Calculate the concentration of solution N in moles per litre. (Relative formula mass of N is 392) (1mark)

(e) Calculate the number of moles of solution N;

(i) In 25cm3 of solution (1mark)

(ii) Which reacts with one mole of potassium manganate (VII) (1mark)

PROCEDURE II

You are provided with:

1. 1.9g of solid P. Solid P is a dibasic acid H2B

2. 0.5.M solution of dibasic acid, H2B. Solution T

3. Sodium hydroxide. Solution R

You are required to determine

(a) (i) the molar heat of solution of solid P

(ii) the reaction of one mole of solid H2B with aqueous sodium hydroxide

(b) Calculate the heat of reaction of solid H2B with aqueous sodium hydroxide

PROCEDURE II (A)

Place 30cm3 of distilled water into 100ml plastic beaker. Measure the initial temperature of the water and record it in

table II below. Add all of solid P at once; stir the mixture carefully with thermometer-until all the solid dissolves.

Measure the final temperature reached and record it in table II

(a) Table II 1½ marks

Final temperature (0C)

Initial temperature (0C)

(b) Determine the change in temperature ∆ T1 ( ½ mark)

Calculate the:

i) Heat change when (H2B) dissolves in water.(Assume the heat capacity of the solution is 4.2jg-10C-1and

density is 1 g/cm3) (2marks)

ii) Number of moles of the acid that were used. (Relative formula mass of H2B is 126) (lmark)

iii) Molar heat of solution ∆ H1of the acid H2B (1mark)

16

PROCEDURE II (B)

Place 30cm3 of solution T into a l00ml plastic beaker. Measure the initial temperature and record it in table III below.

Measure 30cm3 of sodium hydroxide, solution R. Add all the 30cm3of solution R at once to solution T in the beaker.

Stir the mixture with the thermometer. Measure the final temperature reached and record it in the table III.

Table III (1½ marks)

Final temperature (0C)

Initial temperature (0C)

(b) Determine the change in temperature ∆T2 (½ mark)

(c) Determine the:

i) Heat change for the reaction. (Assume the heat capacity of the solution is 4.2jg-10C-1and density is 1 g/cm3)

ii) Number of moles of the acid H2B used. (1mark)

iii) Heat of reaction. 6H2 of one mole of the acid ';hB with Sodium hydroxide (1mark)

(d) Given that:

∆H1 the heat for the reaction H2B(s) Water 2H- (aq) + B2-(aq)

∆H2 the heat tor the reaction 2H- (aq) + 2OH- (aq) 2H2O (l)

Calculate ∆H3 for the reaction H2B(S) + 2OH-(aq) 2H2O(l) + B2- (aq) (2marks)

2. You are provided with solid K: Carry out the tests below and write your observations and inferences in

the spaces provided:

a) Place about half of solid K in a clean dry test tube. Heat the solid gently and then strongly.

Test for any gas produced using both blue and red litmus papers.

OBSERVATIONS INFERENCES

(1 ½ marks) (1mark)

b) Dissolve the remaining solid Kin 8cm3 of distilled water contained in a boiling tube.

Divide the resulting solution into three proportions.


(1 mark) (1mark)

(i) To the first portion, add aqueous Sodium hydroxide dropwise until in excess.



(ii) To the second portion, add two drops of concentrated nitric acid followed by Sodium hydroxide

dropwise until in excess.



(iii) I) To the third portion add 4 drops of Barium Chloride solution


(½ marks) (1mark)

II) To the mixture obtained in (iii)I above, add 2cm3 of 2M aqueous hydrochloric acid


(½ marks) (1mark)

3. You are provided with liquid F. Carry out the tests below.

Record your observations and inferences in the spaces provided.

(a) Place 4 drops of liquid F on watch glass, Ignite the liquid using a Bunsen burner.


(1 mark) (1mark)

(b) To about l cm3 of liquid F in a test-tube, add about 1 cm3of distilled water and shake thoroughly.


(½ marks) (1mark)

(c) To about l cm3 of liquid F in a test-tube, add a small amount of Solid Sodium carbonate.


(½ marks) (1mark)

(d) To about 2cm3 of liquid F in a test-tube, add about l cm3 of acidified Potassium dichromate (VI).

Warm the mixture gently and allow it to stand for about one minute.


(1 mark) (1mark)

17

VIHIGA COUNTY EVALUATION EXAMINATION (EMUHAYA, VIHIGA, SABATIA AND HAMISI) 2013


233/1

CHEMISTRY

PAPER 1

TIME: 2 HOURS

1. Give the appropriate name to describe the following phenomena.

a) Combination of two light unstable nuclides to form one heavy stable nuclide with the release of energy.

(l mk)

b) The minimum amount of energy needed for a reaction to occur. (1mk)

c) The energy required in order for an atom in the gaseous state to lose an electron. (1mk)

2. a) Sulphur deposits are found deep underground and is brought to the surface by pumping down to the ground

hot compressed air and superheated water.

i) What is the purpose of the superheated water? (lmk)

ii) What is the role of the hot compressed air? (Imk)

b) Write a chemical equation to show products formed when a mixture of copper turnings and concentrated

sulphuric (VI) acid are heated.

3. The diagram below shows a setup used to purify copper. Study it and answer the questions that follow.

i) Which electrode should be impure copper? (1mk)

ii) Write the equation for the reaction at the cathode. (l mk)

b) Apart from purification of copper, state two other applications of electrolysis. (1 mk)

4. In an experiment to determine the pH values of various solutions, universal indicator solution

was added to solutions A, B, C and D. The table below shows the results obtained.

Solution Colour obtained

A Orange

B Red

C Purple

D Green

a) Which solution is likely to be ethanoic acid? (lmk)

b) Which solution has the highest concentration of hydroxyl ions per unit volume? (1mk)

c) Select the solution that is likely to be the oxide of hydrogen. (lmk)

5. When a current of 0.82 amperes was passed for five hours through an aqueous solution of a salt of

metal Z, 2.65g of the metal was deposited. Determine the charge on the ion of metal Z (3mks)

(1 Faraday = 96,500C, R.A.M of Z = 52)

6. Element X is in period 2 of the periodic table and forms a stable ion X2+.

a) State the atomic number of element Y which is found directly below X in the periodic table. (lmk)

b) Compare the reactivity of element X and element Y when each is reacted with chlorine. Explain your answer. (2mks)

7. Concentrated nitric (V) acid was added to iron II sulphate solution acidified with dilute Sulphuric (VI)

acid and the mixture heated. The colour of the solution changed from pale Green to yellow and a brown

gas was evolved. Explain these observations. (3mks)

Electrode U

Electrode T

Copper II sulphate

solution

18

8. The diagram below shows a set up used to investigate the process of rusting. Study it and answer the questions that follow.

a) State and explain the observation made on the iron nails in tube B at the end of the experiment. (2mks)

b) State two ways of preventing rusting. (1mk)

9. In the presence of ultra-violet (u.v) light, propane gas undergoes a substitution reaction with bromine.

a) What is meant by the term substitution reaction? (l mk)

b) Give the structural formula and the name of the compound formed when equal volumes of propane

and bromine react. (2mks)

10. When hydrogen gas was passed over heated lead II oxide in a combustion tube, a gaseous product was

obtained. On condensing the gaseous product, a culourless liquid was formed.

a) i) Name the colourless liquid

ii) Which physical test would you use to confirm the identity of the colourless liquid?

b) State the other observation that was made in the combustion tube. (1mk)

c) Write the equation for the reaction in the combustion tube. (1mk)

11. The table below shows the details of the isotopes of element G.

Calculate the relative atomic mass of element G given that the percentage abundance of isotope G I is

10% and that of isotope G2 90% (3mks)

12. Heated iron reacts with both chlorine and hydrogen chloride gases.

a) Write the equation for the reaction of iron with:-

i) Chlorine gas (1 mk)

ii) Hydrogen chloride gas. (l mk)

b) Explain the difference in the oxidation state of iron in the iron compounds formed in (a) above. (l mk)

13. a) State and explain two observations made when a piece of sodium metal is placed into a beaker of water. (2mks)

b) During the extraction of sodium metal from molten sodium chloride, calcium chloride is added to the sodium chloride.

State the role of the calcium chloride. (1 mk)

c) Give two large scale uses of sodium.

14. a) 100g of radioactive 𝑃𝑎91233 decays to 12.5g after 81 days. Determine the half-life of Pa (2mks

b) 𝑃𝑎91233 decays by beta emission. What is the:

i) Mass number

ii) Atomic number of the element formed

15. The diagram below shows a set up used to separate two organic liquids, liquid M(boiling point 56oC) and liquid

N(boiling point 1180C)

a) Identify two mistakes in the above set up. (2mks)

b) State one large scale application of the method of separation shown above. (1mk)

Tube A Tube C

Distilled

water

Iron nails

oil

Boiled

water Iron nails

Cotton wool

Anhydrous Calcium

Chloride

Thermometer

Water in

Liebig condenser

Mixture of

liquid N and

liquid M

Heat

Water out

Distillate

19

16. a) Using dots (•) and crosses (x) to represent outer electrons only, draw a diagram to show the structure

of a nitrogen (N2) molecule. (Atomic number N = 7) (2mks)

b) Explain why nitrogen gas is generally inert. (lmk)

17. 50cm3 of butane (C4H10) is burned in excess of oxygen gas as shown in the equation below.

2C4H10(aq) + 13O2(g) 8CO2(g) + 10H2O(l)

a) Determine the volume of oxygen used. (2mks)

b) Calculate the volume of the gaseous product. (lmk)

18. The table below gives three experiments in which equal amounts of magnesium were reacted with excess dilute

hydrochloric acid under the same temperature and pressure.

In each case the volume of gas produced was recorded over the same time period.

Experiment Form of magnesium Hydrochloric acid solution

I Powder 0.5M

II Ribbon 0.5M

III Turnings 0.5M

On the axis below, draw and label the curves that would be obtained from the above experiments (3mks)

19. The general structure of a certain polymer is shown below.

This polymer has relative molecular mass of 63,000.

Determine the number of monomers in the polymer. (C = 12, H = 1) (2mks)

20. The diagram below shows a set up used to prepare and collect oxygen in the laboratory.

a) Identify solid R. (1 mk)

b) The gas was not collected for the first few seconds of the experiment.

Give the reason why this was done. (1mk)

c) State two commercial uses of oxygen apart from being used by deep sea dives. (l mk)

21. Describe how one can prepare a dry sample of copper II carbonate starting with copper II oxide. (3mks)

22. a) State Charles' law.

b) A fixed mass of a gas has a volume of 200cm3 at 25°C and at a pressure of 101325 Pascal.

What would be its volume at -230C and at 100,000 Pascal? (2mks)

Time (minutes)

Volume of H2 gas (cm3)

Oxygen

Water Solid R

20

23. Compound K reacts with sodium hydroxide as shown below to form compound V

a) Name the type of reaction undergone by compound K (lmk)

b) To what class of organic compounds does compound K belong? (l mk)

c) Explain why compound V is unsuitable for use in washing clothes using water that contains

magnesium sulphate (1mk)

24. The diagram below shows an experiment to study the heating effects of luminous and Non-luminous flames of a

Bunsen burner.

a) What was observed at the bottom of each beaker at the end of the experiment? (1mk)

b) Which sample of water boiled first when the water was heated for the same time period? Explain your answer.

25. a) State the oxide formed under the following conditions:-

i) When charcoal burns in a limited supply of oxygen.

ii) When charcoal burns in excess supply of oxygen. (l mk)

b) State two uses of the oxide in (a) (ii) above. (lmk)

26. The diagram below shows the energy changes that occur during the reaction.

i) State the H sign. Give a reason for your answer. (l mk)

ii) On the same axes, draw an energy level diagram for the reaction when a suitable catalyst is used. Explain the difference in

the shapes. (2mks)

27. You are given the following half-cell reactions.

a) Identify the strongest oxidizing agent. (l mk)

b) Determine the e.m.f of the cell formed when the two half cells are combined. (l mk)

c) Write the equation for the overall cell reaction (l mk)

Glass beaker Glass beaker

A B

100cm3 of

water

21

VIHIGA COUNTY EVALUATION EXAMINATION (EMUHAYA, VIHIGA, SABATIA AND HAMISI) , 2013

233/2

CHEMISTRY

PAPER 2

TIME: 2 HOURS

1. a) Define the term isotopes of an element. (l mk)

b) Study part of the periodic table chart shown below and answer the questions that follow.

The letters do not represent the actual symbols of the elements.

A D E

B C T F G

K H

i) Identify the strongest oxidizing agent. Explain. (2mks)

ii) On the grid, indicate the position of clement X whose ion is X2- and has electron arrangement of 2, 8.

iii) Write a chemical equation for the reaction of element B with water. (1 mk)

c) i) Compare with a reason atomic radius of elements B and G.

ii) Explain observations made when a piece of blue and red litmus papers are placed in a solution of the

chloride of element T.

d) Explain how the melting points of B and C compare.

(1mk)

e) Describe how a mixture of the sulphate of element A can be separated from the carbonate of element K to obtain

the two separate compounds.

(2mks)

f) State two uses of element F

2. a) Define the term solubility of a salt. (l mk)

b) The table below shows results recorded in an experiment carried out to determine the solubility of potassium nitrate.

Temperature (oC) 20 30 40 50 60 70 80 90

Solubility in g per 100g of water 32 46 64 86 110 138 169 202

i) Use the data above to plot a graph of solubility against temperature on the grid provided.

(3mks)

ii) Using the graph determine:

I. Solubility of potassium nitrate at 62oC. (1mk)

II. Molarity of potassium nitrate at 28oC (K = 39, N = 14, O = 16)

iii) What mass of potassium nitrate will crystallize when a saturated solution at 75oC is cooled to 200C.

c) i) On the same axis sketch a graph showing how the solubility of chlorine gas varies with temperature and label it Y.

Explain

ii) State two industrial applications of fractional crystallization apart from its use in study of solubility curves.

c) The table below shows results of four water samples when soap is add cd to each under the stated conditions.


Water sample Drops of soap used to produce lather

Before boiling After boiling

A 20 10

B 3 3

C 15 3

D 20 20

Which sample is likely to be temporary hard water? Explain. (2mks)

e) Using an equation show how ion exchange resin removes hardness from water. (1 mk)

3. The chief ore of aluminium is bauxite, Al2O3. 2H2O.

There are two main stages in the extraction process of aluminium metal namely:-

i) purification of the ore

ii) electrolysis of aluminium oxide

a) i) Identify two main impurities associated with this ore. (1mk)

ii) Describe how the ore is purified to obtain aluminium oxide. (3mks)

22

b) Explain why:-

i) Cryolite is added to molten aluminium oxide at the electrolytic stage. (1mk)

ii) Extraction of aluminium is not done above 20000C. (1mk)

iii) Oxygen gas is produced at the anode during electrolysis of aluminium oxide (1mk)

c) Write an equation for the reaction that produces aluminium. (l mk)

d) Explain two uses of aluminium based on its physical properties. (2mks

e) After a certain period of electrolysis, 132,000 litres of oxygen gas were evolved at the anode according to the equation below.

2O2-(g) O2(g) + 2e-

Calculate the mass of aluminium in kg obtained during the same time.

(Al = 27.0, Molar gas volume at R.T.P = 24000cm3 ) (3mks)

4. Use the standard electrode potentials for elements V, W, X, Y and Z given below to answer the questions that follow.

a) i) What is the E value of the strongest oxidizing agent? Explain.

ii) Which element is likely to be hydrogen? Give a reason. (1 mk)

iii) Draw a labeled diagram of the cell formed when the two half cells of V and X are combined. (2mks)

b) The diagram shows a cross section of a dry cell. Use it to answer the questions that follow.

i) Identify the anode and cathode in this cell. (lmk)

ii) Explain why ammonium chloride and zinc chloride paste and not the dry mixture is used. (l mk)

iii) Write the ionic equations for the reactions taking place at the:- cathode/ anode (l mk)

5. a) Methanol is manufactured by reacting carbon (II) oxide with hydrogen at 3000C and a pressure of 250 atmospheres.

The equation for the reaction is

CO(g) + 2H2(g) CH30H(g)

How would the yield of methanol be affected if the manufacturing process is carried out at 300°C and a pressure of 200

atmospheres? Explain. (2mks)

b) i) The standard enthalpy change of formation of ethanol is - 276kJmol-l.

Write a thermochemical equation for the standard enthalpy change of formation of ethanol. (1mk)

ii) Draw an energy cycle or level diagram and use the information below to determine heat of combustion of

ethanol. (3mks)

23

c) The diagram below shows a set up used to prepare and collect nitrogen (IV) oxide.

i) Write an equation for the reaction that takes place when lead (II) nitrate is heated.

ii) State two observations that would be made in tube S, (2mks)

6. Study the reaction scheme below showing a series or organic reactions and answer the question that follow.

a) Draw the structural formula of compound L and give its IUPAC name (2mks)

b) Identify the type of reaction in step I, II, III, V:-

c) Write an equation to show formation of compound Y from CH2CHCl ( l mk)

d) i) Describe a chemical test that can be used to distinguish between ethanol and ethanoic acid (3mks)

ii) State the conditions for reaction in step (IV) (Imk)

e) i) Write the equation for the reaction that takes place when CaC2 reacts with reagent W. (l mk)

ii) Calculate the volume of gas U in cm3 produced at STP when 20g of CaC2 is completely reacted

with reagent W. (H = 1.0, C = 12.0,O = 16.0, Ca = 40.0, molar gas volume at STP 22.4 litres) (2mks)

24

7. a) The diagram represents arrangement of apparatus used to separate liquid A (boiling point 78°C) and liquid

B (boiling point 100°C) mixture

i) Why is a round bottomed flask preferred for the experiment instead of a flat bottomed flask?

(1 mk)

ii) Name the substance collected first. Explain (2mks)

iii) Name the apparatus labeled F and give its role. (l mk)

iv) What is the use of broken porcelain?

b) The diagram below is a set up by a student in an attempt to prepare dry hydrogen sulphide gas.


i) Identify one mistake in the set up. Explain

ii) Write a chemical equation for the reaction that produces hydrogen sulphide gas (l mk)

iii) State a chemical test for hydrogen sulphide gas.

iv) Explain observation when hydrogen sulphide is bubbled through Zinc (II) sulphate solution. (1mk)

In an experiment sulphur was obtained by reacting moist hydrogen sulphide and sulphur (IV) oxide as shown in the

equation below.

2H2S(g) + SO2(g) 2H2O(g) + 3S(s)

Which of the two reagents is a reducing agent? Explain using oxidation numbers. (3mks)

25

MERU COUNTY FORM FOUR JOINT EXAMINATION, 2013

Kenya Certificate of Secondary Education

233/1

CHEMISTRY

PAPER 1

TIME: 2HOURS 1. The ions R2+ and T- have identical electronic configuration of 2, 8. Write the electronic arrangement of the

elements, (2 marks)

2. The scheme below shows the energy changes that arc involved between ice, water and steam, Study it and

answer the questions that follow

a) What name is given to energy change H4? (1 mark)

b) What is the sign of H2? (Give a reason) (1 mark)

3. Compound Z has the structure.

Name three functional groups in compound Z.

4. a) Identity the type of bond represented by substance R shown below, explain your answer. (2 marks)

b) Predict the group of the periodic table into which R belongs. (1 mark)

5. An organic compound Y was analysed and found to contain carbon, hydrogen and oxygen only. 1.29g of Y on

combustion give 2.64g of carbon (IV) oxide and 0.81g of water. What is the empirical formula of Y?

(C = 12, H = 1, O = 16) (3 marks)

6. Chlorine gas was passed over heated aluminum foil to form substances U as shown below.

a) Identify substance U. (1mk)

b) Write a chemical equation for the reaction which takes place when chlorine and heated aluminium foil react

(1mk)

c) State the property of the product formed in the first combustion tube that makes it possible for it to be collected

in the second combustion tube as shown above. (1 mk)

7. Study the diagram below which shows a cooling curve of substance Z.

a) Identity the region at which the substance is a liquid.

b) From the diagram identity the melting point of Z. (1 mark)

c) At which point among the points A, B, C, D, E and F do molecules of substance Z have

26

i) Lowest kinetic energy. (1 mark)

ii) Lowest intermolecular forces of attraction energy? (1 mark)

8. State and explain what is observed when sulphur (IV) oxide is bubbled through each of the following aqueous

solutions:

a) Acidified potassium chromate (VI)

b) Iron (III) sulphate solution.

9. a) The pH of a sample of soil was found to be 5.0. An agricultural office recommended the addition or

calcium oxide in the soil. State two functions of the calcium oxide in the soil. (2 marks)

b) Give a reason why distilled water is neutral. (1 mark)

10. The following set up of apparatus was used in chemistry lesson aim process. Study it and answer the questions

that follow.

a) Which chemical process was being investigated in this experiment? (1 mark)

b) Before the experiment, the iron filings were first sprinkled with water. Explain why? (1 mark)

c) Give one improvement that need to be included in the set up so as to be able to calculate the percentage

or air used in the process (a) above. (1 mark)

11. Describe how the following reagents can be used to prepare lead (II) sulphate. Solid potassium sulphate,

solid lead (II) carbonate, dilute nitric (V) acid and distilled water. (3 marks)

12. A Student set up the apparatus as shown below to pass an electric current through molten lead (II) iodide.


a) On closing the switch the bulb did not light until a certain condition was met. State the missing condition.(1 mk)

b) State the observations made at the anode when the condition in (a) above was met. (1 mark)

c) Give two reasons why graphite is used as material for electrodes. (1 mark)

13. a) State Boyle's law. (1 mark)

b) On the axis below, sketch the graph of 1/p against volume. (l mark)

c) A given mass of a gas occupies 100cm3 at 700mmHg. Calculate its volume at 720mmHg. (l mark)

14. The scheme below shows the stages in the extraction of zinc from zinc blende.

a) Name process P in chamber II.

b) Write a chemical equation for the reaction taking place at the roasting stage. (1 mark)

c) What is the role of limestone at stage IV? (1 mark)

15. A compound W has the structure shown below.

1/p

27

a) Name the family of compounds to which W belongs. (l mark)

b) State one physical property of W that you would use to recognise it. (1 mark)

c) Name two sources of the compound W above. (1 mark)

16. a) 8.0g of a radioactive clement was reduced to O.5g after 16 hours. Determine the half-life of the element.

(1 mark)

b) A radioactive element W decays as shown below.

Determine the value of a and b. (2 marks)

17. The curve below represents the changes to concentration of substance P and Q with time in the reaction.

P(q) Q(g). Use it to answer the questions that follow.

a) Which curve represents the changes in the concentration of substance Q? (1 mark)

b) What does time’t’ represent in relation to the reaction given? (1 mark)

c) If a catalyst is used in the reaction.

P(q) Q(g).

Indicate on the graph where time (t) would be. (1 mark)

18. A current of 15000 amperes was passed for 1.5 hours in the industrial manufacture or sodium. What

mass of sodium in kilograms was produced? (IF = 96500C, Na = 23.0) (3 marks)

19. Three metal rods A, B and C were first polished (scrubbed with a sand paper) and then dipped into dilute

sulphuric (VI) acid and water as shown below. Study it and answer the questions that follow.

a) Why were the metal surfaces first polished? (1 mark)

b) Arrange the metals in order of their increasing reactivity. (1 mark)

c) Name the gas produced in this experiment.

20. State and explain the observations made when sodium carbonate powder is added to aluminium chloride solution

in water. (3 marks)

21. The diagram below is a set-up used to investigate a certain property of carbon (II) oxide. Study it and answer the

questions that follow.

a) State the observation made in the combustion tube. (1 mark)

b) By use of an equation, explain the observations in (a) above. (1 mark)

28

c) Why should excess gas be burnt at the end of the delivery tube? (1 mark)

22. Compound P has the following structural formula. (1 mark)

a) Name compound P.

b) Write and name the compound formed when P is reacted with chlorine gas. (2 marks)

23. Study the information in the table below and answer the questions that follow. The letters are not the actual symbols of the

elements.

Element Atomic number Melting point oC

L 11 98

M 13 660

N 14 1410

Q 17 -101

a) Explain the difference in melting point of L and M. (1 mark)

b) N forms an oxide with a very high melting point. Explain this observation. (1 mark)

c) Q and L react to form a compound. Does the compound formed conduct electricity in solid state? Explain. (1 mark)

24. The curves below show how electrical conductivity of sulphuric (VI) acid and ethanoic acid vary with concentration.

Explain why the electrical conductivity 0.01M sulphuric (VI) acid is higher than that 0.01M ethanoic acid. (2 marks)

25. 25cm3 of hydrochloric acid was completely neutralised by 30cm3 of a solution containing 5.3g of sodium carbonate per

litre solution. (Na = 23, C=12, O=16)

a) Determine the concentration of sodium carbonate. (1 mark)

b) Calculate the molarity of hydrochloric acid solution. (2 marks)

26. A cleaned magnesium ribbon was burnt in a gas jar of dry nitrogen to form a white powder X.

a) Write an equation for the formation of powder X. (1 mark)

b) Powder X was dissolved in water to give a solution Y and gas Z.

i) State the effect of solution Y on litmus. (1 mark)

ii) Name gas Z. (1 mark)

27. a) What is allotropy? (1 mark)

b) Consider the scheme below for allotropes of sulphur.

Allotrope J Allotrope K

i) What is the significance of temperature 96°C? (1 mark)

ii) Name allotrope J and K. (1 mark)

28. Below are molar enthalpies of combustion of propane, hydrogen and carbon.

a) Write the equation for the formation of propane from it elements. (1 mark)

b) Determine the molar enthalpy of formation of propane. (2 marks)

96oC

29



233/2

CHEMISTRY

Paper 2

Time 2hours 1. Use the following electrode potentials to answer the questions below. (1 mark)

a) From the list above, identify;

i) The strongest oxidising agent. (1 mark)

ii) The strongest reducing agent (1 mark)

b) A cell using zinc and lead was set up as shown.

i) Write the equation for the cell reaction. (1 mark)

ii) Calculate 𝐸𝜃 for the cell. (1 mark)

iii) What is a suitable salt bridge for this cell? (1 mark)

iv) Explain how the salt bridge helps to maintain the charge balance in each half-cell as the reaction continues. (2 marks)

c) i) Using a labelled diagram, explain how a copper spoon can be electroplated with silver. (2 marks)

ii) Calculate the amount in grammes of silver that would be deposited on the spoon in two hours using a current

of 0.03 amperes. (Charge of 1 mole of electrons = 96500 coulombs) (Ag = 108) (2 marks)

d) Select two elements from the list in (1) above that would make a cell with the minimum electromotive

force. (1 mark)

2. a) Study the diagram below and answer the questions that follow.

i) Write an equation for:

I. The reaction between CH3 COONa and NaOH. (1 mark)

II. The complete burning of gas P. (1 mark)

ii) Give a reason why sodium hydroxide is mixed with calcium oxide to make sodalime. (1 mark)

iii) State and explain the observations made when gas P is bubbled through bromine water under normal

laboratory conditions. (2 marks)

iv) Name the homologous series to which gas P belongs. (1 mark)

b) Study the flow chart below and answer the questions. (2 marks)

Draw and name compound X.

c) Below are two reactions showing how a lung-chained carboxylic acid can be converted to detergent C.

30

i) Name each of the types of reactions.

ii) State one disadvantage of using detergent C in washing clothes with hard water. (1 mark)

3. The diagram below shows the extraction of sulphur from underground.

a) State the substances which are passed through A and B and explain how each assist in the extraction of sulphur.

b) A sample of the extracted sulphur is heated in air.

I. Write an equation for the reaction when sulphur burns. (1 mark)

II. State and explain the observations made when wet blue litmus paper is dropped in a gas jar containing

product in b(l) above. (2 marks)

c) i) Name two reagents used to prepare hydrogen sulphide gas. (1 mark)

ii) Name two physical properties or hydrogen sulphide gas. (1 mark)

iii) State and explain the observations made when dry hydrogen sulphide gas is passed through a tube containing

dry sulphur (IV) oxide. (2 marks)

4. In an experiment, 5.0cm3 portions of 1.OM potassium hydroxide were added to 20.0cm3 of 0.5M oxalic acid

solution in a beaker. The mixture was stirred with a thermometer and temperature taken after each addition of

potassium hydroxide. The readings obtained were recorded as shown in the table below.

Volume of 1M KOH (cm3) 0 5 10 15 20 25 30 35 40

Temp of mixture (oC) 25.0 25.8 27.0 28.0 29.0 29.0 26.5 23.0 21.5

a) Plot a graph or temperature (y-axis) against volume of potassium hydroxide on the grid provided. (3 marks)

b) From the graph determine;

i) Volume of potassium hydroxide required to completely neutralize 20.0cm3 of the 0.5M oxalic acid, a

dibasic acid H2C204 (l mark)

ii) The highest temperature change. (l mark)

c) Calculate the heat change for the reaction (Take specific heat capacity of the solution to be 4.2.Jg-1k-1 and

density to be 1.0g/cm3. (2 marks)

d) Calculate the moles of oxalic acid used in the reaction. (1 mark)

e) Calculate the molar heat of neutralization of oxalic acid. (2 marks)

f) Apart from heat loss to the surrounding, give two other source errors that may have affected the actual

molar heat of reaction. (2 marks)

5. The grid below is part of the periodic table of elements. The symbols used arc not the actual symbols of the

elements. Study it and answer the questions that follow.

31

A

B G E

L C

D

Y F

i) What name is given to the family of elements to which A and C belong? (1 mark)

ii) Write the chemical formula of sulphate of L. (l mark)

iii) The ionic radius of Element E is bigger than its atomic radius. Explain. (2 marks)

iv) The oxide of G has lower melting point than oxide of L. Explain. (2 marks)

v) Among element B, G, E which one has the highest 1st ionisation energy? Explain. (2 marks)

vi) Which letter from the table represents.

a) The strongest oxidizing agent (1 mark)

b) The strongest reducing agent. (1 mark)

vii) State and explain one commercial use of clement C. (2 marks)

6. The diagram below illustrates the hall-herdt cell used in electrolysis of aluminium oxide during the extraction of

aluminium metal. Study it and answer the questions that follow.

a) What is the name of the ore from which aluminum is extracted? (1 mark)

b) Name any two impurities found in the ore. (I mark)

c) State role of cryolite added to aluminium oxide. (1 mark)

d) High temperatures must be maintained during the electrolysis process. State a disadvantage caused by the high

temperature. (2 marks)

e) Other than density state one other property of aluminium that makes it possible to be collected as shown

in the diagram. (1 mark)

f) Why is it cheaper to recycle aluminium other than extracting it using the method shown above? (1 mark)

g) The scheme below shows the stages of extraction of copper metal from its ore (Copper pyrites).

i) Write an equation for the reaction taking place at the roasting stage. (1 mark)

ii) The copper from the converter is not pure. Draw a labelled diagram to show the set-up you would use

to refine the copper by electrolysis. (3 marks)

iii) State two properties of copper which make it suitable for use in making currency coins. (1 mark)

7. a) The diagram below shows a set-up by a student for the separation of liquid P and Q whose boiling points are

35°C and 91°C respectively. Liquid P is very inflammable.

32

i) State one error the student made in setting up the experiment. (1 mark)

ii) Name apparatus R. (1 mark)

iii) What method of separation is used by the student? (1 mark)

iv) Why is it possible to use the method named in (iii) above to separate P and Q? (I mark)

b) The chromatogram below represents the results of an experiment done with certain plant pigment.

Study it and answer the questions below.

i) Name two pure pigments.

ii) Which two pigments shown above can be mixed to form pigment S?

iii) State two reasons which makes substance U cover a longer distance on the chromatogram than T. (l mark)

c) Study the flow chart below and answer the questions below it.

i) Identify gas X (1 mark)

Ii) Write an equation for the reaction between the white precipitate and excess gas X. (1 mark)

Iii) State a possible identity of solid P. (1 mark)

33



233/3

CHEMISTRY

Paper 3


- 0.1 M sodium hydroxide, solution A

- 1.5g of solid B which is a carboxylic acid (C2H3O2)n

You are required to prepare a solution of solid B and use it to determine the value of n in (C2H3O2)n

Procedure

Place all the solid B in a 250ml volumetric flask. Add about 200cm3 of distilled water. Shake the mixture well

and add distilled water to make up to the mark. Label this solution B.

Fill the burette with solution B.

Using a pipette and pipette filler place 25cm3 of solution A into a 250ml conical flask. Add two drops of the

phenolphthalein indicator provided and titrate with solution B. Record your results in the table below.

Repeat the titration two more times and complete the table. (4 marks)

I II III

Final burette reading (cm3)

Initial burette reading (cm3)

Volume of solution B (cm3)

a) Calculate;

i) The average volume of solution B used. (1 mark)

ii) The number of moles of sodium hydroxide used. (1 mark)

iii) The number of moles in the volume of solution B used.

Mole ratio of solution A: Solution B is 2 : 1 respectively. (1 mark)

v) The molar mass of (C2H3O2)n (1 mark)

vi) The value of n. (C=12.0, O=16.0 and H=1.0) (2 marks)

2. a) You are provided with 5.0g of solid C in a boiling tube. Perform the experiments below to determine the

solubility of solid C at various temperatures.

Experiment (i)

Using a measuring cylinder, measure 5cm3 of distilled water and add it to the boiling tube containing solid C.

Insert a thermometer into the boiling tube and heat the mixture until ALL the solid dissolves. Allow the

solution to cool while. Stirring gently with the thermometer. Note the temperature at the which crystals of

solid C first appear. Record the temperature in the table below. Retain the boiling tube and its contents for

the experiment below.

Experiment (ii)

Add 2cm3 of water to the same boiling tube from experiment 1 above. Heat the mixture until all the solid

dissolves. Allow the solution to cool while stirring with the thermometer and record the temperature at which

crystals first appear. (The cooling of the solution can be speeded up by dipping the boiling tube into a beaker

of cold water for a few seconds and removing it.

Experiment (ii)

By adding 2cm3 of water at a time, to the same boiling tube, repeat procedure for experiment 2 and complete

the table for experiments (iii), (iv) and (v)

Table 2

Experiment Total volume of Temperature at which crystals Solubility of solid C of

water (cm3) first appear oC per 100g water

i) 5

ii) 7

iii) 9

iv) 11

v) 13

b) On the grid provided, plot a graph of solubility (vertical axis) against temperature. (3 marks)

i) Solubility of solid C at 45°C (l mark)

ii) Volume of water that would be required to dissolve 5g of solid C at 60°C to make a saturated solution.

(Density of water = l gcm3) (l mark)

34

3. a) You are provided with solid D. Carry out the tests below and write your observations and inferences in the

spaces provided.

i) Place all the solid D provided into a boiling tube. Add about 10cm3 of distilled water and shake well. Divide

the resultant mixture into four portions.

Observation Inference

(1mk)

(1mk)

ii) To the first portion add 2M sodium hydroxide dropwise until in excess.


(1mk)

(1mk)

iii) To the second portion, add aqueous ammonia dropwise till in excess.


(1mk)

(1mk)

iv) To the third, add 5 drops of Sodium sulphate solution


(1mk)

(1mk)

v) To the fourth portion, add 3 drops of barium nitrate solution and retain the mixture for test (vi) below.


(1mk)

(1mk)

vi) To the mixture in (v) above, add about 5cm3 of 2M nitric (V) acid.


(1mk)

(1mk)

b) You are provided with solid E. Use it to carry out the tests below

i) Take a small amount of solid E on a metallic spatula and ignite it on a Bunsen burner flame.


(1mk)

(1mk)

ii) Take the remaining solid E and place it into a boiling tube. Add about 15cm3 of distilled water and shake

well. Divide the resulting solution into three portions.

I. to the first portion add 3 drops of bromine water.


(1mk)

(1mk)

II. To the second portion, add solid sodium hydrogen carbonate.


(1mk)

(1mk)

III. To the third portion in a test-tube, test its PH using universal indicator paper.


(1mk)

(1mk)

35

GEM DISTRICT FORM FOUR JOINT EVALUATION TEST, 2013


233/1

CHEMISTRY

Paper 1

Time: 2 hours

1. Give two reasons why Helium is used in weather baloons. (2 marks)

2. The table below shows the pH values of solutions I, II, III and IV.

Solution I II III IV

pH 2 7 11 14

a) Which solution is likely to contain a higher concentration of hydroxide ions? (1 mark)

b) Select the solutions in which a sample of aluminium oxide is likely to dissolve. Give a reason for you answer. (2 marks)

3. Aluminium Chloride sublimes at about 1800C, while Aluminium Oxide melts at 18000C.

a) State the types of bonding in each of the two compounds: Aluminium Oxide /Aluminium Chloride

b) Explain why the sublimation temperature of Aluminium Chloride is lower than the melting point of Aluminium Oxide.

(2 marks)

4. Copper (II) Carbonate was heated as shown in the set up below. Study the diagram and answer the questions that follow

State and explain the observations made in

i) Tube A ii) Tube B 5. A sample of hard water was divided into options and analysed. The results of analysis were tabulated as shown below.

Portion of water Observations on treatment of water with

Na2CO3(aq) Pb(NO3)2(aq) Ba(NO3)2(aq)

Unboiled water White precipitate White precipitate No precipitate

Boiled water White precipitate White precipitate No precipitate

a) Predict the type of hardness in the water (I mark)

b) Suggest the compound likely to be present in the water. (I mark)

6. During a class experiment Chlorine gas was bubbled into a solution of Sodium iodide.

a) State the observations made (2 marks)

b) Using an ionic equation, explain why the reaction is redox. (2 marks)

7. a) State Boyle's law . (I mark)

b) On the axes below, sketch a graph of pressure against volume. (I mark)

c) Explain the shape of the curve in terms of kinetic theory.

8. The thermochemical reaction between carbon and sulphur is as shown by the equation below.

C(s) + 2S(s) CS2(l) H = +117.0kJ/mol On the grid below, sketch and label the energy level diagram for the reaction. (3 marks)

9. The product formed by the action of heat on nitrates of elements A, B, and C are shown below.

Nitrate Products formed

A Metal oxide + Nitrogen (IV) oxide + Oxygen

B Metal + oxygen + Nitrogen (IV) oxide

C Metal Nitrite + Oxygen

a) Arrange the metals in increasing order of reactivity (1 mark)

b) i) Which element forms a soluble carbonate (1 mark)

Volume

Pressure

36

ii) Give an example of metal B (1 mark)

10. Lead (II) Carbonate was added a little at a time to 50cm3 of 3M nitric acid until no further change was observed.

The mixture was then filtered. The filtrate was divided into two parts X and y. - Part X was evaporated carefully on a water bath until dry. A solid residue was left.

- Part Y was warmed until concentrated and then kept in an evaporating dish overnight. A solid was observed.

a) What observation was made on the solids formed? (2 marks)

b) Explain the observations in X, Y:- (2 marks)

11. Study the information below and answer the questions that follow

Solvent

Solid Water Alcohol Either

Alum Soluble Insoluble Insoluble

Camphor Insoluble Soluble Very soluble

Sugar Soluble Soluble Insoluble

Describe how you would obtain a solid sample of sugar from the mixture (3 marks)

12. a) 100g of radio-active 23391

𝑝𝑎 was reduced to 12.5g after 81 days. Determine the half-life of Pa

b) 23391

𝑝𝑎 decays by beta emission. What is the mass number and atomic number of the element formed? (1 mark)

13. Study the information below and answer the questions that follow

Number of Carbon atoms per molecule Relative molecular mass or hydrocarbon

2 28

3 42

4 56

a) Write the general formula of the hydrocarbon in the table

b) Predict the relative molecular mass of the hydrocarbon with 5 carbon atoms

c) Determine the molecular formula of the hydrocarbon in (b) and draw its structural formula (H = 1, C = 12.0) (2marks)

14. Study the scheme below and answer the questions that follow

a) Write the formula of the cation present in solution F (1 mark)

b) What property of chlorine is shown in step I? (1 mark)

c) Write an equation for the reaction which occurs in step III. (1 mark)

15. In an experiment, ammonium chloride was heated in a test tube. A moist red litmus paper placed at the mouth of the test tube first

changed blue then red. Explain these observations. (3 marks)

16. A hydrocarbon contains 87.8% carbon and its molecular formula is 84. Determine its empirical formula and molecular formula.

(3 marks)

17. A crystalline organic compound X reacted with concentrated sulphuric (VI) acid in the presence of a few drops of water to produce

a black mass substance S. After washing and drying, substance S was reacted with hot concentrated sulphuric (VI) acid to produce

two colourless gases

a) Name the type of reaction between

i) X and the concentrated sulphuric (VI) acid ii) S and concentrated sulphuric (VI) acid

b) Suggest the identities of substance X and S. (2 marks)

18. Study the information below and answer the questions that follow. The letters do not represent actual symbols of

the elements.

Element Atomic Mass Melting point °c

L 11 97.8

M 13 660

N 14 1410

Q 17 -101

R 19 63.7

Step I Cl2(g)

FeSO4(aq)

Yellow solution Brown solid Step II

Solid X + water

Addition of NaOH(aq) and

filter Step III Heat

37

a) Write the electronic arrangement for the

i) Ion of element M (1 mark)

ii) Atom of Q (1 mark)

b) Select an element which is

i) The most reactive non-metal (l mark)

ii) A poor conductor of electricity (1 mark)

19. Study the flow chart below and answer the questions that follow.

a) Identify;

i) Solid P.

ii) Solution Q

b) Write an equation leading to the formation of

solution Q. (1 mark)

c) Write the formula of the complex ion

present in solution R (1 mark)

20. a) Hardness of water may be removed by either boiling or addition of chemicals. Write one equation to show how

boiling removes hardness of water. (1 mark)

b) Explain why permanent hardness in water cannot be removed by boiling. (2 marks)

21. Calculate the amount of Calcium Carbonate that would remain if 15.0g of calcium carbonate were reacted with 100cm3 of

2M hydrochloric acid. (Ca = 40, C = 12, O = 16). (3 mark)

22. Equal volumes of air were passed through concentrated sodium hydroxide and then over heated copper turnings and hot

magnesium separately. The table below shows the volumes of nitrogen gas obtained after sometime.

Metal Volume of nitrogen (cm3)

Copper 20

Magnesium 5

a) What was the role of concentrated sodium hydroxide solution? (1 mark)

b) Explain the difference in the remaining volumes of nitrogen. (2 marks)

23. Equal volumes of 2M Sodium hydroxide and 2M ethanoic acid were mixed. With explanation, estimate the pH of the final

solution. (2 marks)

24. a) State Gay Lussac's Law (1 mark)

b) 10cm3 of a gaseous hydrocarbon C2HX. required 30cm of oxygen for complete combustion. If 20cm3 of steam and

20cm3 of carbon (IV) oxide were produced, what is the value of X? (2 marks)

25. a) Name one natural fibre (l mark)

b) Give two advantages of synthetic fibres over natural fibres (2 marks)

26. Dilute sulphuric (VI) acid was added to lead (II) carbonate in a test tube. State and explain the observations that

were made. (2 marks)

27. The set-up shown below was used to investigate a property of hydrogen gas.

State and explain the observations that would be made in the glass tube if beaker A was filled with hydrogen gas.

38



233/2

CHEMISTRY

Paper 2

Time: 2 hours

1. The grid below shows part of the Periodic Table. Study it and answer the quest ions that follow. The letters do not represent the

actual symbols.

A

B C D E

F G

H

a) Which element forms ions with charge of 2? Explain. (2 marks)

b) What is the nature of the oxide formed by C? (1 mark)

c) How does the reactivity of 11 compare with that of L? Explain (2 marks)

d) Write down a chemical equation for the reaction between B and chlorine (1 mark)

e) How does the atomic radii of F and G compare? Explain (1 mark)

f) If the oxides of F and D are separately dissolved in water, state and explain the effects of their aqueous solutions on litmus

paper. (3 marks)

2. I. The flow chart below show the various stages of water treatment. Study it and answer the questions that follow

i) What substances are likely to be removed in Filtration unit I? (1 mark)

ii) What is the name of process Y? (1 mark)

iii) What is the purpose of:

a) Process Y?

b) Addition of sodium hydrochlorite? (1 mark)

iv) It was confirmed that magnesium sulphate was present in the tap water.

a) What type of hardness was present in the water? (I mark)

b) Explain how the hardness can be removed. (2 marks)

II. In an experiment to synthesize sodium carbonate in the laboratory, students passed carbon (IV) oxide and ammonia gas into

brine as shown in the flow diagram below. Use it to answer the questions that follow.

i) Why is the mixture obtained in chamber A cooled in chamber B? (2 marks)

ii) Give a reason why it is difficult to synthesize potassium carbonate by the same method. (1 mark)

iii) State two properties of carbon (IV) oxide that enables it to be used in fire extinguishers. (2 marks)

3. a) Two ores of alluminium are bauxite Al2O3.2H2O and China clay Al2SiO7.H2O. Suggest two reasons why bauxite is usually

preferred to China clay for extraction of aluminiun.

b) Aluminium metal is extracted from its ore according to the scheme shown below. Study the scheme and answer the questions that

follow.

39

i) Iron (III) oxide and silicates are the main impurities. Identify the chambers where each of these impurities is removed.

I) Iron (III) oxide

II) Silicates

ii) Explain the function of sodium hydroxide solution (1 mark)

iii) Write the formula of the anion present in filtrate F. (1 mark)

iv) Write the equation for the reaction in kiln G (1 mark)

v) Give the name of solid H and state its function. (2 marks)

c) Give two properties of aluminium or its alloys which make it useful in making sufurias. (2 marks)

d) Explain why it is difficult to extract aluminium metal by reduction of its oxide. (1 mark)

4. Butane is a gas at room temperature and pressure. It is used to melt bitumen to apply on roads.

a) Write the equation for complete combustion of butane (1 mark)

b) Define the term standard enthalpy ofcombustion. (1 mark)

c) The set-up below was used to determine the enthalpy of combustion of butane.

In the set up 200cm3 of water were used. The temperature of the water changed from 22oC to 70oC when 1g butane burn

completely in oxygen.

i) Calculate the heat energy produced in kJ. (2 marks)

(Specific heat capacity of water = 4.2kJkg-llkl, density of water = 1gcm-3)

ii) Calculate the molar enthalpy change of combustion of butane. (C=12, H=1) (2 marks)

iii) Calculate the heating value of butane (1 mark)

iv) Given the following data:

Ho (carbon) = -393 kJmol-1

HCo (hydrogen) = -286 kJmol-1

HCCo (butane) = -2320 kJmol-1

I. Draw an energy cycle diagram for the formation of butane. (2 marks)

II. Using the energy cycle diagram in (I) above, calculate the enthalpy of formation of butane (2 marks)

5. I. Use the scheme below to answer the questions that follow.

a) i) Name the type of reaction in step I (1 mark)

ii) Give the reagent and condition necessary for the reaction in step I to take place. (1 mark)

b) Write the equation for the reaction that takes place in step II. (1 mark)

c) i) Name product B and give the conditions necessary for its formation. (2 marks)

ii) State the characteristic property of compounds to which product B belongs (1 mark)

40

d) Describe one chemical test for Gas D in the laboratory. (1 mark)

II. Use the diagram below to answer the questions that follow.

a) Name substances M and P (1 mark)

b) Explain how the above cleansing agent improves the cleansing property of water. (1 mark)

c) Give one advantage of this cleansing agent over ordinary soap. (1 mark)

d) Name the other type of detergent besides the one synthesized above. (1 mark)

6. The following set-up was used to investigate electrolysis of magnesium sulphate solution.

i) Identify electrodes A and B: (1 mark)

iii) Explain the differences in volumes of gases P and Q. (2 marks)

iv) Explain what happens to the concentration of magnesium sulphate during electrolysis. (1 mark)

b) Use the data below to answer the questions that follow.

Half reaction 𝐸𝜃(V)

Mg2+(aq) + 2e- Mg(s)

Ag+(aq) + e- Ag(s)

Cu2+(aq) + 2e- Cu(s)

Ni2+(aq) + 2e- Ni(s)

-2.38

+0.80

+0.00

-0.25

i) Identify the reference electrodes. (1 mark)

ii) From the above list, identity the strongest oxidising agent. Explain. (1 mark)

iii) Workout the e.m.f of the two half-cells that when connected will produce the largest e.m.f (1 mark)

iv) Draw a hydrogen half- cell (2 marks)

v) Can a solution of silver nitrate be stored in a nickel container? Give a reason for your answer. (2 marks)

7. Use the information in the table below to answer the questions that follow.

Mass of KCl (g) Volume of water (cm3) Temperature at which

crystals first appear (oC)

Solubility g/100g H2O

Centre 20 40 77

Centre 20 45 56

Centre 20 50 40

Centre 20 55 26

Centre 20 60 15

Centre 20 65 8

a) Calculate the values of solubility. (2 marks)

b) Plot the solubility curve for potassium chloride. (4marks)

c) If a saturated solution of potassium chloride is cooled from 500C to 100C, what mass of crystals would be obtained? (1 mark)

d) State any two uses of solubility curves. (2 marks)

c) What is the effect of temperature on the solubility of potassium chloride in water? (1 mark)

f) 2% of sea-water is Sodium Chloride. Calculate the mass of sea -water used to produce 170tonnes of Sodium chloride.

(2 marks)

41



233/3

CHEMISTRY

Paper 3

Time: 2 ¼ HOURS


- 0.4 M hydrochloric acid solution F

- 0.4 M Sodium Hydroxide solution G

- 1.59g of X,CO solid M.

You are required to determine the R.A.M of X in solid M

Procedure:

Measure accurately 100cm3 of solution F into a clean beaker and put all the solid M into this solution. Shake the mixture

until all the solid has dissolved and no more effervescence occurs. Label this solution H. Fill the burette with solution G

and pipette 25 cm3 of solution H into a conical flask and add 3 drops of phenolphthalein indicator.

Titrate solution H with solution G until a permanent colour change occurs. Repeat the titration two more times to obtain

consistent results.

Table I

1 2 3



Volume of Solution G used (cm3)

(4 marks)

a) Determine the average volume of solution G used. (1 mark)

b) Calculate the number of moles of Hydrochloric acid in 100 cm3 of solution F. (1 mark)

c) Calculate the number of moles of Sodium hydroxide in the average volume calculated in (a) above. (1 mark)

d) Calculate the number of moles of hydrochloric acid in 25cm3 of solution H. (1 mark)

e) Calculate the number of moles of hydrochloric acid in 100cm3 of solution H, (1 mark)

f) How many moles of hydrochloric acid reacted with solid M? (1 mark)

g) Given that the equation of the reaction between solid M and hydrochloric acid is

X2CO3(s) + 2HCl(aq) 2XCl(aq) + H2O(l) + CO2(g)

i) Calculate the number of moles of solid M which reacted with hydrochloric acid. (2 marks)

ii) Determine the relative molecular mass of solid M (C= 12, O=16) (2 marks)


- Solution R Sodium hydroxide solution

- Solution S a solution containing 38g/dm3 of an acid H2C204. XH20.

Procedure

Measure 30cm3 of solution S using a measuring cylinder and place it in a clean 100cm3 beaker.

Measure the temperature of the solution and record it in the table below.

To this solution, 10cm3 portions of solution R stirring gently and measuring the maximum temperature reached

after each addition.

Record your values in Table II below.

Table II

Volume of solution R added (cm3) 0 10 20 30 40 50 60 70

Total volume of mixture (cm3)

30 40 50 60 70 80 90 100

Maximum Temperature (0C)

(5 marks)

a) Plot a graph of maximum temperature (y - axis) against the total volume of the mixture (x=axis). (3 marks)

b) From the graph, determine;

i) The highest temperature change T (1 mark)

ii) The volume of R that will neutralise 30cm2 of S. (1 mark)

c) Given that H = MCT kJ and the molar heat of neutralisation for the reaction is 57.3 kJmol-1.

where m = mass of mixture, C = 42Jg-1k-l T = change in temperature. Assume the density of the solution to Be 1 gcm3.

i) Calculate the heat change at neutralisation point of the reaction. (1 mark)

2NaOH(aq) + H2C2O.XHO4(aq) Na2C2O4(aq) + 2H20(l) +XH2O(l)

42

ii) How many moles of Sodium hydroxide (solution R) are used in the reaction? (1 mark)

iii) What is the molarity of solution S? (1 mark)

iv) Calculate the molar mass, relative formula mass and hence find the value of "X" in H2C2O.XH2O (3 marks)

3. a) You are provided with solid E. Carry out the following tests on it and record your observations and inferences in the

spaces provided.

Place all the solid E into a boiling tube. Add about 20cm3 of distilled water and shake until the solid dissolves. Label the

solutions as E. Use solution E for experiments below.

Divide solution E into four portions.


(½ mark) (½ mark)

i) To the first portion add dilute NaOH dropwise until in excess.


(1 mark) (1 mark)

ii) To the second portion, add dilute NH3 dropwise until in excess


(1 mark) (1 mark)

iii) To the third portion, add a few drops of HCl and shake the mixture


(1mark) (1 mark)

iv) To the fourth portion add a few drops of barium nitrate


(½ mark) (½ mark)

b) You are provided with liquid H,

Carry out the following test and record your observations and inferences in the spaces provided below.

i) Dip a dry clean glass rod in the liquid H and immediately place the wet rod to a non- luminous flame.


(1mark) (1 mark)

ii) To about 2cm3 of liquid H, add two-three drops of acidified potassium manganate (VII).


(1mark) (1 mark)

c) To about 4cm3 of liquid H, add two to three drops of bromine water and warm the mixture.


(1mark) (1 mark)

43

EMBU COUNTY FORM 4 COMMON EVALUATION, 2013


233/1

CHEMISTRY

Paper 1

Time: 2 hours 1. Describe how an acid base indicator can be made in the laboratory using purple cabbage leaves. (2 marks)

2. Study the table below giving some particles and answer the questions that follow. The letters do not represented

the actual symbols of the elements.

Particles Protons Electrons Neutrons

A 10 10 10

B 15 18 16

C 11 10 12

D 9 9 12

E 10 10 11

a) Which of the letters represented,

i) Anion. (1 mark)

ii) Cation. (l mark)

b) Which of the letters represents isotopes. Explain. (l mark)

3. a) Name one compound responsible for temporary hardness of water.

b) State two large scale uses of hard water. (2 marks)

4. State the set-up below and answer the questions that follow.

a) Identify the gas generated in the above set up. (1 mark)

b) Why is it necessary to use an inverted funnel in the beaker? (1 mark)

5. a) Phosphorous has an atomic number of 15. State the type of bond formed when phosphorus combines

with bromine. (l mark)

b) Using dot (•) and cross (x) diagram, show the bonding in ethane molecule. (Atomic No. of C = 6, H=1).

(l mark)

6. A compound C3H8O reacts with sodium metal, forming a basic solution and a colorless gas.

a) To which class of organic compounds does it belong? (1 mark)

b) Identify the;

i) The basic solution. (l mark)

ii) The colourless gas. (1mark)

7. A glass tube was inserted into a flame formed when air hole of the Bunsen burner was fully open as shown in the

figure below.

a) When a burning splint was brought near point P, a small name lit at this end of the glass tube. Explain. (1 mark)

b) Give two main reasons why the Bunsen burner flame above is preferred for heating than the flame obtained

when air hole is closed. (1 mark)

8. A mass of 40g of a saturated solution of potassium chlorate at 25°C yields 14g of potassium chlorate

when evaporated to dryness. Calculate the solubility of potassium chlorate at 25°C. (2 marks)

44

9. The table below shows the formulae of the chloride of P, Q R and S (not the actual symbols)

Element P Q R S

Formula of chloride PCl QCl2 RCl3 SCl5

a) State the group to which the elements P, Q, R and S belong. (2 marks)

b) State the bond type formed in PCl and SCl5. (1 mark)

10. Zinc powder is added to a boiling tube containing copper (II) sulphate solution.

a) State one observation made.

b) Using an ionic equation, explain why the reaction in a redox. (2 marks)

11. Study the diagram of the set-up below and answer the questions that follow.

a) Identify the colour of the flame at point P. (l mark)

b) Describe a chemical test for liquid X. (2 marks)

12. Carbon (IV) oxide can undergo the changes shown below.

CO2(s) CO2(g)

a) What are processes A and B. (2 marks)

b) Suggest one use of carbon (IV) oxide that utilizes processes A and B. (1 mark)

13. Xg of sodium hydroxide were dissolved in distilled water to make 100cm2 of solution. 50cm3 of this solution

required 50cm3 of 2M nitric (V) acid for complete neutralization. Calculate the mass X of sodium hydroxide

dissolved. (Na= 23, O=16, H=l) (3 marks)

14. a) State the Avogadro's principle (1 mark)

b) Calculate the volume of oxygen that will be required for complete combustion of l00cm3 of carbon(II)oxide.

What is the volume of the carbon(IV) oxide formed? All volumes are taken at the same temperatures and

pressure. (2 marks)

15. a) A mixture of calcium powder and silver powder was reacted with dilute hydrochloric acid. The solution was

filtered.

Name

i) The filtrate (1 mark)

ii) The residue (1 mark)

b) Write an ionic equation for the reaction that takes place. (1 mark)

16. Describe how you would prepare a sample of lead(II)sulphate using the following reagents:

Dilute sulphuric (VI) acid, dilute nitric (V) acid and lead carbonate. (3 marks)

17. In an experiment, chlorine gas was passed into moist hydrogen sulphide gas as shown below.

a) What observation was made in the boiling tube? (1 mark)

b) Write an equation for the reaction which took place in the tube. (1 mark)

c) What precaution should be taken when carrying out this experiments? Give a reason. (1 mark)

18. Uranium -238 undergoes a radioactive decay according to the equation.

𝑈92238 𝑍𝑦

𝑥 + 𝐻𝑒 + 2 𝑒−10

24

a) Determine the value of x and y (l mark)

b) Q grams of a radioactive isotope sample takes 80 days to disintegrate to 7g. The half-life of the isotope is 20

days. Find the initial mass Q. (2 marks)

19. a) Apart from iron ore (haematite), name two other raw materials fed into the blast furnace in the extraction

of iron metal (1 mark)

A

B

45

b) Write an equation to show how the ore is reduced in the blast furnace. (1 mark)

c) Suggest one use of iron. (1 mark)

20. The set-up below was used to prepare and collect a sample of oxygen gas.

a) Complete the set up. (1 mark)

b) Name solid Z ....................................................................................................................................... (I mark)

c) Write an equation for the reaction that occurs in the flask. (1 mark)

21. 14.82 g of a hydrocarbon contains 12.2g of carbon. Find the simplest formula of the hydrocarbon.

(C = 12, H = 1.0) (3 marks)

22. Study the flowchart below and use it to answer the questions that follow.

a) Write the formula of cation in solution K. (I mark)

b) What property of the white ppt is illustrated in Step I and II. (I mark)

23. a) Define the term heating value of a fuel. (1 mark)

b) Calculate the heating value of ethanol if molar enthalpy of combustion for ethanol is -1360KJmol-1

(C=12, O=16) (1 mark)

24. The atomic radii generally decreases across a period and increases down the group, Explain. (2 marks)

25. a) State Graham's Law of diffusion (1 mark)

b) 50cm2 of ear bon (IV) oxide diffuses through a porous plate in 15 seconds. Calculate the time taken

by 75cm3 of nitrogen (IV) oxide to diffuse through the same plate under similar conditions.

(C=12, O=16, N=14) (2 marks)

26. Helium, neon and argon are in group (VIII) of the periodic table.

a) Give one use of helium other than filling of air craft tyres. (1 mark)

b) Other than density give one reason why helium is used to fill aircraft tyres. (1 mark)


a) Identify substance Q. (1 mark)

b) Write an equation leading to formation of R. (1 mark)

28. a) What do you understand by the term isomers? (1 mark)

b) Draw the isomers of the compound C3H7Cl and give their systematic names. (2 marks)

29. The diagram below shows how molten copper (II) chloride can be e1ectrolyscd using graphite e1ectrodes.

46

a) Why are graphite electrodes preferred in the above set-up? (1 mark)

b) Why is the experiment done in a fume chamber? (1 mark)

c) What would be observed at the cathode? (1 mark)

30. The reaction of phenolphthalein indicator in water may be represented as follows.

HPh(aq) + H2O(l) H3O+(aq) + Ph-

(aq)

a) State and explain the observations made when an acid is added to the equilibrium mixture. (1 mark)

b) Two experiments on the reaction of excess hydrochloric acid and 2.0g of marble chips were done under different

conditions. In each case the volume of gas was recorded at different intervals.

Experiment Conc HCl

a lumps of marble chips 2.0M

b powdered marbles chips 2.0M

On the same axis, draw and label the two curves that could be obtained from the above results. (2 marks)



233/2

CHEMISTRY

Paper 2

Time: 2 hours

1. The diagram below represents the extraction of sulphur from its underground deposits by the

Frasch process. Study the diagram and answer the questions that follow.

i) Name the substances that pass through pipes L, M, N. (3 marks)

ii) What is the purpose of the substances that passes through pipes L and M? (2 marks)

iii) State two uses of sulphur. (1 mark)

b) The flow chart below shows the preparation of carbon (II) oxide and its reactions.

47

i) Name the type of reaction taking place between oxalic acid and concentrated sulphuric VI acid. (1 mark)

ii) Why is the gaseous mixture passed through concentrated potassium hydroxide? (1 mark)

iii) Write an equation for the production of solid B and gas C. (1 mark)

iv) State one use of carbon IV oxide. (1 mark)

c) 4.6g of a compound made up of carbon, hydrogen and oxygen was completely burnt in excess oxygen

8.8g of Carbon IV oxide and 5.4 of water were formed at the end of the experiment. Determine the simplest

formula of the compound. (C = 12, H=l, O=16)

2. An unknown mass of calcium carbonate was reacted with excess 2M hydrochloric acid. The volume of the gas

produced was recorded after each minute as shown in the table below

Volume of the gas (cm3) 0 27 46 62 72 78 82 82 82

Time in minute 0 1 2 3 4 5 6 7 8

a) Plot a graph of volume of the gas against time. (3marks)

b) From the graph; Determine:

i) The rate or reaction of time t = 4½ minutes. (2 marks)

ii) The maximum volume of the gas produced. (1 mark)

c) i) Write down the equation for the reaction between calcium carbonate and dilute hydrochloric acid. (1 mark)

ii) Determine the mass of calcium carbonate that reacted

(molar gas volume at room temperature = 24dm3; Ca = 40, C=12, O=16) (2 marks)

d) The equation below shows a dynamic equilibrium between X2(g) and Y2(g)

X2(g) + 3Y2(g) 2XY3 H = -ve

i) How would the yield of XY3 be affected if the pressure is decreased? Explain.

ii) How would the use catalyst affect the yield of XY3? Explain.

3. Study the table below showing properties of elements across period three then answer the questions that follow.

Element A B C 0 E F G U

Atomic radius (nm) 0.156 0.136 0.125 0.118 0.11 0.104 0.099 -

Ionic radius (nm) 0.095 0.065 0.050 - - 0.184 0.181 -

Melting point (oC) 97.8 650 660 1410 44.2 119 -101 186

i) Explain why the atomic radius of G is smaller than its ionic radius. (1 mark)

ii) How does the melting point of D and E compare? Explain. (2 marks)

iii) What type of bond exists in the chloride of C? (1 mark)

b) The ions V3+ and U2- have the electronic configuration 2,8. Give the electronic arrangement of the atoms of

elements:

c) The grid below represents part of the periodic table. The letters used are not the actual chemical symbols.

Use it to answer the questions that follow.

G

H I J

K M N 0 P Q R T

i) Name the family of elements to which elements K and P belong.

ii) Choose a letter from the grid which represents the lightest gas.

iii) Which of the elements from the grid above would form an ion with the charge -1? Explain. (2marks)

iv) How do the reactivity of J and N compare? Give a reason for the answer. (2 marks)

4. a) Use the standard electrode potentials for elements A, B, C, D and E given below to answer the questions that

follow. The letters do not represent the actual symbols of the elements.

Standard electrode potentials E(volts)

A2+(aq) + 2e- A(s) -2.90

B2+(aq) + 2e B(s) -2.38

C(aq) + e ½ C2(g) 0.00

D2+(aq) + 2e D(s) +0.34

½E(2)(g) E(aq) -2.87

i) Which element is likely to be hydrogen? Give a reason for your answer. (2 marks)

ii) What is E value of the strongest reducing agent? (1 mark)

iii) In the space provided, draw a labelled diagram of the electrochemical cell that would be obtained when half cells

of elements B and D are combined. (2 marks)

iv) Calculate the E value of the e

48

b) During the electrolysis of aqueous copper II sulphate using copper electrodes, a current of 0.2A was passed

through the cell for 5 hours.

i) Write an ionic equation for the reaction that took place at the anode (1 mark)

ii) Determine the change in mass of the anode which occurred as a result of the electrolysis process.

(Cu=63.5, IF=c96500C) (2 marks)

5. a) Name the following compounds.

b) Study the scheme below and answer the questions that follow.

i) Identify the products B, F.

ii) State the conditions for step I

iii) Name the compounds; C, E

iv) Write the equation for the reaction leading to the formation of methane. (1 mark)

v) State two industrial uses of methane. (2 marks)

vi) Identify the reagent D. (1 mark)

vii) Name the type of reaction in Step I. (1 mark)

6. a) i) The extraction of aluminium takes place in three stages. Identity any 2 stages. (1 mark)

ii) Name the main ore from which aluminium is extracted and the impurities associated with it.

Main ore:

Impurities:

iii) What is the role of sodium hydroxide in the extraction of aluminium (1 mark)

iv) Why is electrolysis chosen as the method of extraction in obtaining aluminium from its ore?

(1 mark)

v) From the method of extraction mentioned in (V) above.

I. Write chemical equation for the reaction at the electrodes. Anode and Cathode (2 marks)

II. Why are the carbon anodes replaced regularly? (1 mark)

b) i) Name the principal ore from which copper is extracted . (1 mark)

ii) Which method is used to concentrate the copper ore before its roasted? (1 mark)

iii) After smelting, the impure copper metal is purified by electrolysis.

I. Draw a diagram of a circuit that can be used for this process.

II. Give one alloy of copper. (1 mark)

III. Other than making alloys, state one use of copper

7. The following set-up by a form four student intended to measure the heat of combustion of methanol.


The results are as shown below.

49

Initial temperature of water = 21.5°C

Final temperature of water = 30.0°C

Initial mass of bottle + methanol = 85.10g

Final mass of bottle + methanol = 84.78g

Specific heat capacity of water = 4.2kJ/Kg/oC

a) Use the results above to calculate the molar heat of combustion to methanol, CH3OH.

(C = 12, H = 1, O = 16) (3 marks)

b) Is this reaction endothermic or exothermic? Explain. (2 marks)

c) The accurate (theoretical) value of heat of combustion of methanol is -638kJ/moles.

How does this value compare with the one in (a) above? Explain. (2 marks)

d) Write the thermochemical equation of combustion of methanol. (1 mark)

e) Draw on the axis below energy level diagram to show the reaction in (i) above. (2 marks)



233/2

CHEMISTRY

Paper 2

July / August, 2013


- Solution A

- Solution B (2M NaOH)

You are required to determine the heat of reaction per mole of A used using the procedure below.

NB- PRESERVE SOLUTIONS A AND B FOR USE IN QUESTION 2.

PROCEDURE

i) Fill the burette with solution A

ii) Using a measuring cylinder, put 20cm3 of solution B into the plastic beaker provided.

iii) Add 4cm3 of solution B from the burette and determine the highest temperature (ToC) attained.

iv) Continue adding 4cm3 portions of solution B and every time determining the highest temperature (ToC)

attained.

v) Fill the highest temperature (ToC) attained in the table I below. (5 marks)

Vol of solution A (cm3) 4 8 12 16 20 24 28 32

ToC obtained (oC)

a) Plot a graph of volume of solution A used against highest temperature (ToC) of solution attained (3marks)

b) Determine the volume of solution A that react completely with solution B. (1 mark)

c) From the graph, determine the initial temperature of solution A. (I mark)

d) Determine the temperature change when solution B is completely reacted with solution A. (1 mark)

e) Determine the heat evolved when the reaction is complete (Density of solution 1 g/cm3, S.H.C. of solution

is 4.2 j/g/k.) (2 marks)

f) Determine the heat of reaction per mole of solution A used. (2 marks)

50

2. Using the solutions A and B preserved in Q1, you are required to determine the basicity of the acid A using the

procedure below.

Procedure

Pipette 25.0cm3of solution B and titrate against solution A in the burette using methyl orange indicator and fill in

the table below. (4 marks)

Table II

I II III



Volume of solution A used (cm3)

a) Determine the average volume or solution A used. (1 mark)

b) Determine the concentration of solution B in moles / dm3(Na 23, O=16, H=1) (2 marks)

c) Calculate the number of moles of NaOH in 25cm3 of solution. (1 mark)

d) Calculate the number of moles of acid in the average volume of solution A obtained. (1 mark)

e) Determine the basicity of acid A. (1 mark)

3. You are provided with solid K. Carry out the tests below and write your observations and inferences in the

spaces provided.

a) Place 1/3 spatula full of solid K in a boiling tube. Heat gently and then strongly. Test the gases produced with

litmus papers.


(1mark) (1mark)

b) Dissolve the remaining solid K in about 6cm3 of distilled water. Divide it into 3 portions.

i) To the first portion, add dropwise sodium hydroxide till in excess.


(1mark) (1mark)

ii) To the second portion, add 2cm3 of acidified lead (II) nitrate solution


(1mark) (1mark)

iii) To the third portion, add 5 props of aqueous sodium hydroxide. Add a piece of aluminium foil

provided to the mixture and shake. Warm the mixture and test any gas produced with both

blue and red litmus paper.


(2mark) (1mark)

c) You are provided with solid L. Carry out the tests below and record your observations and inferences in

spaces provided.

Dissolve solid L in about 6cm3 of distilled water and divide the solution into 3 portions.

i) To the first portion, add 3 - 4 drops of KMnO4 and warm


(1mark) (1mark)

ii) To the second portion, add about 0.5g sodium hydrogen carbonate.


(1mark) (1mark)

iii) To the third portion, add 2cm3 of universal indicator.


(1mark) (1mark)

51

GUCHA SOUTH FORM FOUR JOINT EVALUATION EXAM, 2013


233 / 1

CHEMISTRY

PAPER 1

TIME: 2 HOURS

1. The table below gives melting and ionization energies on metallic elements A, Band C. The metals are arranged as they occur

in the periodic table.

Element Melting points(0C) First ionization energy KJ/mol-1

A -180 520

B 98 496

C 64 419

a) Which of these elements is the strongest reducing agent? (1mark)

b) Are these elements members of the same group or period? (1mark)

2. A gas at 270C and 750 mmHg pressure was found to occupy 36cm3. Calculate the temperature at which the same mass of gas

will occupy twice the volume at a pressure of 1000 mmHg pressure. (3marks)

3. The graph below represent the solubility curve of a gas in water.

a) State and explain the conclusion that can be drawn from the curve about the solubility of the gas. (2marks)

b) The solubility of potassium chlorate at 800C is 40 per 100g of water. What mass of potassium chlorate will saturate

65g water at 800C? (2marks)

4. The diagram below shows a set lip that was used to prepare and collect a sample of nitric acid.

a) Give a reason why it is possible to separate nitric acid from sulphuric acid in the set- up? (1mark)

b) Name another substance that can be used instead of potassium nitrate. (1mark)

c) Give one use of nitric acid. (1mark)

5. Fractional distillation of liquid air usually produces nitrogen and oxygen as the major products.

i) Name one substance that is used to remove carbon (iv) oxide from the air before it is changed into liquid. (1mark)

ii) Describe how nitrogen gas is obtained from the liquid air.

(Boiling points of nitrogen = -1960C, oxygen = 1830C) (2mark)

6. In an experiment, equal amounts of magnesium powder were placed into test tube 1 and 2 as shown below.

Temp (oC) So

lub

ilit

y i

n g

/10

0g

of

H2O

52

Explain why the amount of hydrogen gas liberated in test-tube 2 is greater than in test-tube 1 before the reaction

is complete. (2marks)

7. When wood is burnt, a grey powder called ash remains. The ash is stirred with water and filtered, a colourless

solution is obtained.

a) What is the main component of the colourless solution? (1mark)

b) Explain your answer in (a) above. (2marks)

8. A compound contains 12.84% by mass of carbon, 2.14% hydrogen and the rest Bromine

a) Calculate its empirical formula. (C= 12, H=1, Br =80). (2marks)

b) Calculate its molecular formular if its relative molecular mass is 188. (1mark)

9. a) What is an amphoteric hydroxide? (1mark)

b) Write an equation to explain the term amphoteric oxide. (2marks)

l0. a) Distinguish between hydrogen bond and van der waals forces of attraction. (2marks)

b) Using two water molecules, draw a diagram to show the difference between hydrogen bond and covalent

bond. (1mark)

11. 0.5 moles of hydrogen chloride gas was dissolved in water and the solution made up to one litre. 30cm3 of this

solution was found to neutralize exactly 25cm3 of a solution of sodium carbonate. The equation for the reaction

is as follows:

Na2CO3(aq) + 2HCl 2NaCl (aq) + H2O(l) + CO2 (g)

Calculate the concentration of the carbonate in moles per litre. (3marks)

12. Study the information below and answer the questions that follow.

Mg Cl2 (s) Mg2+ (g) + 2Cl- (g) ∆H1 = -2489KJmol-1

Mg Cl (s) + (aq)→ Mg Cl2 (aq) ∆H2 = -5142KJ mol-1

2Cl (g) + (aq) → 2Cl- (aq) ∆H3 = -762 KJ mol-1

a) Give the specific names of the enthalpies DHI and DH2. (1mark)

b) Determine the enthalpy for the reaction. (3marks)

Mg2+ (g) + (aq) → Mg2+ (aq)

13. In the Harber process for the production of ammonia, hydrogen and nitrogen react according to the following

equation.

N2(g) + 3H2(g) 2 NH3(g) ∆H = -92KJ.

a) Name the catalyst used in the above process. (1mark)

b) Explain how the following changes would affect the yield of ammonia.

I) Decrease in pressure. (1mark)

II) Increase in temperature. (1mark)

14. Steam was passed over iron fillings as shown in the diagram below.


a) State one precaution which should be taken before lighting the gas at the jet. (1mark)

b) Write a chemical equation for the reaction taking place:-

i) in the combustion tube (1mark)

ii) at the jet (1mark)

15. A solution of silver nitrate was put in a container made of metal Q for 1 day. Given that:

Q2+(aq) + 2e- Q (s) E0 = -0.13V.

Ag+(aq) + e Ag (s) E0 = +0.80V.

Determine whether or not a reaction occurred between silver nitrate and metal Q. (2marks)

16. 100cm3 of gas A takes 30 seconds to diffuse through a porous plug whereas 300cm3 of oxygen takes 120

seconds. Calculate the relative molecular mass of gas A. (O =6) (3marks)

17. Zinc occurs naturally as Zinc blende (Zns) and calamine (Zn CO3).

a) Name the three substances that are used to concentrate the ore of zinc by froth floatation. (1½ marks)

b) The ores are initially converted to the oxides by roasting in air.

Heat

53

i) Why is it necessary to convert the ores into the oxides? (1mark)

ii) Write the equation for the reaction which occurs when calamine is roasted in air. (1mark)

18. Study the set up below and answer the questions that follow.

a) State the observations that were made. (1mark)

b) Explain the observations that were made. (1mark)

c) Write an equation for the reaction that took place in the beaker. (1mark)

19. The diagram below shows part of a given polymer. Study it and answer the questions that follow.

a) Write down the formula of the monomer from which the polymer is derived. (1mark)

b) If the polymer has a molecular mass of 45762g, estimate the number of monomers in the polymer.

(C = 12, H =1) (2marks)

20. Describe how a solid sample of zinc carbonate can be prepared from zinc oxide, dilute sulphuric (vi) acid and sodium

carbonate crystals. (3marks)

21. Complete the following table by filling in the missing test and observations. (3marks)

No Gas Test Observation

I Chlorine Put moist red litmus into the gas

II Sulphuric (iv) oxide Paper turns green

III Butane Add a drop of bromine water

22. In an experiment, ammonium chloride was heated in a test-tube. A moist red litmus paper placed at the mouth of the test

tube first changed blue then red. Explain these observations. (3marks)

23. Y grams of a radioactive isotope take 120 days to decay to 3.5grams. The half-life period of the isotope is 20 days.

a) Find the initial mass of the isotope. (2marks)

b) Give one application of radioactivity in agriculture. (1mark)

24. The reaction between hot concentrated sodium hydroxide and chlorine produces sodium chlorate (v), sodium chloride and

water.

a) Write an equation for the reaction (1mark)

b) Give one use of sodium chlorate. (1mark)


Name:

a) While precipitate A. (1mark) b) Solution B. (1mark) c) Gas C. (1mark)

26. Study the information in the table below, and answer the questions that follow.

No. of atoms per molecule Relative molecular mass of hydrocarbon

5 70

6 84

7 98

a) Name the homologous series of members represented in the table above. (1mark)

b) Draw the structural formula of the seventh member of the above series and write its name (2marks)

27. The set up below was used to demonstrate the effect of heat on hard water.

54

a) Name substance A. (1mark)

b) Explain why the heating of hard water produces substance A. (2marks)


233 / 2

CHEMISTRY PAPER 2

Time: 2 hours 1. In an experiment to determine molar heat of displacement, excess zinc was added to a plastic beaker containing

100cm3 or 0.5 M copper (II) sulphate and the solution was stirred with a thermometer, the temperature of the

solution changed from 210C to 45.50C.

(Zn 65, s.h.c = 4.25Jg-1 K-I, density = 1 g/cm3)

a) State and explain the observations made. (2marks)

b) Calculate;

i) Moles ofCuSO4 in the solution. (1mark)

ii) Heat of reaction. (2marks)

iii) Molar heat of displacement. (1mark)

c) i) Explain why excess zinc were used. (1mark)

ii) Determine the mass of zinc that was used.

(1mark)

d) Write the thermochemical equation and ionic

equations. (1mark)

e) The theoritical value is greater than the experimental

value. Account for the difference. (1mark)

f) Draw an energy level diagram. (2marks)

2. Students wanted to prepare and collect dry Hydrogen chloride gas in the laboratory using NaCl.

a) Name the other regent used in the preparation and state the condition required. (1mark)

b) Draw the apparatus used in the experiment. (2marks)

c) Write an equation for the reaction that occurred in the flask. (1mark)

d) State how one can test for the presence of the gas. (1mark)

e) i) State 2 reasons why common salt (NaCl) is the chloride of choice. (1mark)

ii) Explain with an equation, why Barium chloride is not suitable for replacing common salt (NaCl) in the

reaction; Write an ionic equation for the reaction (2marks)

f) i) Draw a diagram of apparatus used to make a solution of Hydrogen chloride gas. (1mark)

ii) Describe how chloride ions are tested; Write an ionic equation for the test. (2marks)

3. Study the flow chart below and use it to answer the question that follow.

a) Identify the cation and anion in solution K.

i) Cation (lmark) ii)Anion ................................................................ (lmark)

b) i) Name precipitate L. (lmark)

ii) Write the ionic equation for the formation of precipitate L. (lmark)

c) i) Name the type of reaction in step 2. (lmark)

ii) Write a balanced equation for the reaction in step 2. (1mark)

d) i) Write the formula of colourless solution M is step 1. (1mark)

ii) Write the equation for the complex ion in solution M. (1mark)

e) i) Write the ionic equation for the reaction in step 3. (1mark)

ii) Write the chemical equation in step 3. (1mark)

4. A) A current of 2A was passed for 30 minutes through a solution containing ions of metal P and deposits

3.92g of metal P. (IF = 96500c, P = 207)

a) Calculate the quantity of electricity used. (lmark)

b) Determine the quantity of electricity that could deposit 1 mole of metal P. (1mark)

c) i) Determine the charge of metal P. (lmark)

ii) Write the equation for the reaction at the cathode. (lmark)

55

B) Use the reduction potentials below to answer the question that follow.

Zn2+(aq) + 2e Zn(s) E = -0.76V

Cu2+(aq) + 2e Cu(s) E = +0.34V

Fe2+(aq) + 2e Fe(s) E = -0.44V

a) i) Draw an electrochemical cell formed when copper half-cell is combined with zinc half-cell. (2marks)

ii) Write half equation and overall equation for the cell formed. (lmark)

iii) Write the cell representation/cell notation for the cell. (lmark)

iv) Calculate the Emf of the cell reaction. (lmark)

b) State the functions of a salt bridge. (lmark)

c) i) Write half equation and overall equation for the cell formed between zinc and iron. (lmark)

ii) Explain why zinc is used to galvanise iron. (lmark)

5. Study the flow chart below and answer the questions that follow

a) Identify reagent B. (lmark)

b) Write the equation for the reaction taking place in step 1. (lmark)

c) Identify substance K. (lmark)

d) What names are given to processes in the following steps (2marks)

i) Step 2 ii) Step 3 iii) Step 4 iv) Step 5

e) State the condition necessary for step 2. (1mark)

f) Draw and name the structural formula of substance T and R.

i) Substance T. (1mark) ii) Substance R. (1mark)

g) Write equation for the reaction in step 3. (1mark)

h) State the 2 uses of product T. (1mark)


a) Explain using equations how sulphur (IV) oxide is obtained in contact process. (2marks)

b) Identify solid K. (1mark)

c) i) Suggest impurities present in the gaseous mixture and how they are eliminated. (1mark)

ii) Give reasons of purifying the gaseous mixtures. (1mark)

iii) Identify the 2 catalysts that can be used in the catalytic chamber. (1mark)

iv) Which of the catalysts is preferred? Give reasons. (1mark)

d) Why is sulphur (IV) oxide not absorbed directly into distilled water. (1mark)

e) Write down an equation for the reaction that takes place in the catalytic chamber. (1mark)

f) Write down an equation for the reaction taking place in the:

i) Absorption tower, (1mark) ii) Dilute (1mark)

g) i) Name the pollutants in the contact process. (1mark)

ii) Name the 2 methods by which pollution is controlled in contact process. (1mark)

7. Hydrogen peroxide decomposes to water and oxygen when a little manganese (IV) oxide is added to the solution.

The-results are given in the following table.

Volume of oxygen (cm3) 0 19 27 33 36 38 39 40 40

Time (sec) 0 10 20 30 40 50 60 70 80

a) i) What is the role of manganese (V) oxide in the reaction? (1mark)

56

ii) Write the equation for the reaction. (1mark)

b) i) Plot a graph of the volume of oxygen produced against time (sec) (4marks)

ii) Determine the rate at the 20th sec. (2marks)

iii) Why is the curve steeper at the start of the reaction? (1mark)

c) When do the reaction come to an end? Explain. (1mark)



233 / 3

CHEMISTRY

Paper 3

1. You are provided with:-

- Solution L containing S.6g per litre of anhydrous sodium

carbonate.

- Solution M;

- Hydrochloric acid.

- Phenolphthalein Indicator.

- Methyl orange indicator.

57

You are required to standardise the Hydrochloric acid solution M.

Procedure

Fill the burette with solution M. Pipette 25cm3 of solution L into a conical flask. Add three drops of phenolpthalein

indicator and titrate with solution M. DO NOT POUR OUT THE CONTENTS OF THE CONICAL FLASK. Record the

readings in table I below. Add 3 drops of methyl orange indicator to the contents of the conical flask and continue

titrating with solution M. Record the readings in table II below. Repeat the procedure and complete tables I and II.

TABLE 1 (USING PHENOLPHALEIN INDICATOR)

I II III



Volume of solution M used (cm3)

(4marks)

a) Find the average titre t1 (1mark)

TABLE II (USING METHYL ORANGE INDICATOR)

I II III

Final burette reading (cm3) Initial burette reading (cm3)

Volume of solution M used (cm3)

b) i) Find the average titre t2: ......................................................................................... . ................................. (1mark)

b) ii) Find the total volume of solution M used. (t1 + t2,) ..................................................................... (1mark)

iii) Calculate the concentration of Sodium carbonate in moles per litre. (Na = 23.0, C = 12.0, O =16.0) (1mark)

iv) Calculate the moles of sodium carbonate in 25cm of solution. (lmark)

3. b) Place a little of substance F in a boiling tube. Add about 8 cm3 of distilled water and shake well.

i) Place about 2 cm3 of solution F in a test tube and determine its pH.


(1mark) (1mark)

ii) Place about 2cm'3 of solution F in a clean dry test tube and add a spatula end full of Sodium Carbonate.


(1mark) (1mark)

iii) To about 2 cm'3of solution F in a test tube add acidified Potassium dichromate (vi) and warm.


(1mark) (1mark)

iv) To about 2 cm'3 solution F in a test tube add acidified Potassium Manganate (vii) and warm.


(1mark) (1mark)

v) Add Bromine water to about 3 cm'3 of solution F in a test tube and warm.


(1mark) (1mark)

58

KAJIADO COUNTY JOINT EXAMINATION, 2013


233/1

CHEMISTRY

PAPER 1

Time: 2 hours

l. a) A solution of sodium carbonate was found to contain soluble calcium and magnesium salts.

Explain how sodium carbonate can be used to purify the solution. (2mks)

b) State one use of sodium carbonate (lmk)

2. Study the table below and answer the questions that follow. The letters do not represent the actual symbols of

the elements.

Element Atomic radius (nm) Ionic radius (nm)

P 0.114 0.195

Q 0.072 0.136

R 0.133 0.216

S 0.099 0.181

Do the elements form part of metallic or non-metallic group? Explain (2mks)

3 a) When a hydrocarbon was completely burnt in oxygen, 8.4g of carbon (iv) oxide and 3.42g of water

were formed. Determine the empirical formula of the hydrocarbon (C = 12, H = 1) (3mks)

b) Given that its relative molecular mass is 28, work out the molecular formula of the hydrocarbon. (lmk)

4. Explain why the boiling point of iodine is much higher than that of chlorine. (2mks)

5. Aluminium is extracted from its ore by the process of electrolysis. a) Name the chief ore from which aluminium

is extracted. (lmk)

b) Aluminium is separated from its impurities in form of sodium aluminate. Write an equation that shows how

sodium aluminate is formed.

6. When 8.53g of sodium nitrate were heated in an open test tube, the mass of oxygen gas produced was 0.83g.

Given that the equation for the reaction is

2NaNO3(aq) 2NaNO2(s) + O2(g)

Calculate the percentage of sodium nitrite formed (Na = 23.0, N = 14.0, O = 16.0) (2mks)

7. The curve below represents the changes in the concentration of nitrogen (IV) oxide and dinitrogen tetraoxide

with time in the reaction:

2NO2(g) N2O4(g)

a) Which curve represents the changes in concentration of dinitrogen tetraoxide? Give a reason. (2mks)

b) Give a reason for the shapes of the curves after time 't' minutes . (lmk)

8. Ammonia is a raw material in the industrial manufacture of nitric (v) acid.

a) Briefly explain how ammonia is converted to nitrogen (ii) oxide. (2mks)

b) Determine the oxidation number of nitrogen in NH+ 4 (lmk)

9. Below are the bond dissociation energies of some elements.

Bond Bond dissociation energy

C-C 343 kjmol-1

C-H 414 kjmol-1

H-H 435 kjmol-1

C(s) C(g) 711 kjmol-1'

Use this information to calculate the heat of reaction for (3mks)

2C(s) + 3H2(g) C2H6(g)

10. 14.2g of sodium nitrate saturated 32.1cm3 of water at 32°C. Determine the solubility of sodium nitrate

at 32°C. (Density of water = 19/cm3) (2mks)

11. Study the electrode potential in the table below and answer the questions that follow.

Time

Concentration

Mol / dm3

59

a) Identify the strongest agent. (1 mk)

b) Write the electrochemical equation for the reaction that takes place when copper wire is dipped in a solution of

silver nitrate. (lmk)

12. Study the nuclear equation below and answer the questions that follow.

𝐶614 𝑁7

14 + 𝑄𝑦𝑥

a) Identify particle Q b) Determine the values of x and y. (2mks)

13. Study the scheme below and answer the questions that follow.

a) Identify: (3mks)

i) Solid Q

ii) Substance B

iii) Substance M

iv) Process I

v) Process II

vi) Substance T

b) Substance T is mixed with substance M and warmed with a few drops of concentrated sulphuric (vi)

acid. Write a chemical equation for the reaction that occurs. (l mk)

14. A known volume of ozonised oxygen diffuses through a small hole in 55 seconds; whereas the same amount of

oxygen mixed with chlorine takes 67 seconds under the same conditions. Determine

the molecular mass of ozone. (Cl = 35.5; O = 16) (3mks)

15. Write the discharge equations (half equations) for the electrode reactions when molten sodium chloride is

electrolysed using graphite electrodes.

Anode (1mk) Cathode (1mk)

16. When carbon (iv) oxide gas was passed through aqueous calcium hydroxide solution, a white suspension is

formed.

a) Write an equation for the reaction that took place. (1 mk)

b) State the explain the change that would occur when excess carbon (iv) oxide gas is bubbled through

the white suspension. (2mks

17. The table below gives some information about a certain chemical substances. The letters used are not the actual

chemical symbols or formula.

substance Melting point oC Boiling point oC Electrical conductivity

Of solid Of liquid In water

A

B

C

D

E

F

1540

-114

712

-39

2045

1700

3000

-85

1418

357

3000

2776

Good

Poor

Poor

Good

Poor

Poor

Good

Poor

Good

Good

Good

Poor

Insoluble

Good

Good

Insoluble

Insoluble

Insoluble

a) From the table, select-

i) Two substances that cannot be elements. (lmk)

60

ii) A substance that is likely to have giant atomic structure. (1mk)

iii) A substance that is likely to consist of molecules and which produce ions when added to water. (1mk)

18. An element W has three isotopes, A having 25 neutrons, B 21 neutrons and C 18 neutrons.

If the relative abundances of A, B and C are 18, 10 and 2 respectively and the number of protons

of W is 20, calculate the relative atomic mass of W. (2mks)

19. Study the scheme below and answer the questions that follow

a) Write an equation for the formation of the white fumes. (lmk)

b) Suggest a suitable test for gas E. (lmk)

c) Identify solid A. (lmk)

20. Nitric (v) acid reacts with copper (ii) oxide, according to the equation below;

CuO(s) + 2HNO3(aq) Cu(NO3)2(aq) + H2O(l)

0.75g of impure copper (ii) oxide reacted with 100cm3 of 0.15M nitric (v) acid. Calculate the

percentage of copper (ii) oxide in the impure sample assuming that the impurities did not react

with the acid. (3mks)

21. Complete the diagram below for the preparation of dry hydrogen sulphide gas.

b) State two observations made when hydrogen sulphide gas is bubbled through concentrated nitric (v) acid.

(lmk)

22. a) Propane reacts with oxygen according to the equation given below;

Calculate the volume of propane that would produce 1000kJ of heat when completely burnt.

(Molar volume of a gas at r.t.p = 24 litres) (2mks)

b) Give the structural formula of propyne. (lmk)

23. In an experiment, dry hydrogen chloride gas was passed through heated iron powder as shown in the diagram

below. The gas produced was then passed through heated lead (ii) oxide.

a) State the function of the water in flask T. (lmk)

b) Write the equation tor the reaction that occurs in tube I (lmk)

c) State and explain the observations made in tube II. (2mks)

61

24. In a class experiment, a student prepared Nitrogen (i) oxide gas in order to investigate its properties.

a) Name the reagents used in the preparation of Nitrogen (iv) oxide gas. (2mks)

b) State one property of Nitrogen (iv) oxide gas that facilitates its transportation to industries. (lmk)

25. The table below gives factors that affect the rate of the reaction between zinc granules and 2.0M

hydrochloric acid:

Zn(S) + 2HCl(aq) ZnCl2(aq) + H2(g)

Complete the table to show how each factor affects the rate of reaction and give an explanation for

each effect. (3mks)

Factor Effect on rate of reaction Explanat

ion Heating the reactants

Addition of copper (ii) sulphate crystals

Using O.2M HC) acid

26. In the manufacture of sulphuric (vi) acid, some of the sulphur (iv) oxide gas is not converted to sulphur (vi)

oxide, instead it is released to the atmosphere.

a) Explain how sulphur (iv) oxide forms acid rain. (lmk)

b) In an attempt to control environmental pollution, Mazingira Chemical Company passed sulphur (iv)

oxide gas through concentrated nitric (v) acid. Explain the observations made. (2mks)

27. Below is a sketch of a reaction profile.

a) On the diagram, show the heat of reaction H. b) State and explain the type of reaction represented by the profile. (2mks)

28. The diagram below shows a set up that was used to prepare and collect a sample of nitric (v) acid

a) Write an equation for the reaction that occurs in the round bottomed flask. (lmk)

b) State one property of concentrated nitric (v) acid that enables it to react with both metals and

non- metals. (lmk)

c) Suggest a suitable apparatus that can be used instead of the round bottomed flask. (lmk)

Reaction path

62



233/2

CHEMISTRY PAPER 2

TIME: 2 HOURS

1.

c) Describe why the liquid becomes dark and viscous. (2mks)

d) Sulphur reacts with both concentrated nitric (v) acid and concentrated sulphuric (vi) acid.

i) No reaction occurs when sulphur is added to concentrated hydrochloric acid and warmed.

Explain why? (lmk)

ii) State the observations made when sulphur reacts with concentrated nitric (v) acid. (lmk)

iii) Write an equation for the reaction that occurs between sulphur and concentrated sulphuric (vi) acid. (lmk)

e) Sulphur is oxidized to sulphur (iv) oxide by oxygen gas. In an experiment on oxidation, form three

students found out that 3 litres of oxygen gas oxidized a fixed amount of sulphur to sulphur (iv) oxide

at room temperature and pressure. Determine the volume of sulphur (iv)oxide formed.

(Molar gas volume at r.t.p =24dm3) (S = 32, O= 16) (2mks)

2. a) State Hess's law. (lmk)

b) Use the following equations to answer the questions that follow.

i) Draw an energy cycle diagram for the formation of butane. (2mks)

ii) Calculate the heat of combustion of butane. (lmk)

c) Distinguish between hydration energy and lattice energy. (2mks)

d) The diagram below shows an energy level diagram for the dissolution of magnesium chloride.


i) State the enthalpy changes represented by. H1, H2, H3 (3mks)

ii) What is the relationship between H1, H2, H3 (lmk)

iii) Calculate the enthalpy change H1 given that: H2 = +2484 Kj/mol, H3 = -2695 kj/mol (lmk)

e) i) Define heating value. (lmk)

ii) Give two reasons why charcoal and wood fuel are chosen for domestic use . (lmk)

iii) Suggest one safety measures that should be taken when transporting and marketing L.P.G gas.(lmk)

3. The reaction scheme below represents the process of extracting iron metal from one of its chief ores, iron pyrite

(FeS) and the preparation of iron (ii) sulphate crystals. Study it and answer the questions that follow.

a) i) Write down the equation for the reaction that occurs in the roasting chamber. (lmk)

ii) Name the following substances.

Gas W (lmk) Solid X ................................................ (lmk)

63

iii) Explain how carbon (ii) oxide used to reduce the oxide of iron is obtained. (2mks)

iv) Write the equation for the reaction in which iron is formed. (lmk)

v) Due to high temperatures in the blast furnace, limestone decomposes to carbon (IV) oxide and calcium oxide.

Explain the importance of calcium oxide using an equation. (lmk)

b) Describe how crystals of iron (ii) sulphate can be obtained in step I starting with iron filings. (2mks)

c) Gas V is a pollutant. Modern industrialists use scrubbing method to prevent escape of the gas to the

atmosphere. Explain how this method works. (lmk)

d) i) State one commercial use of slag. (lmk)

ii) Name two industries which can be located near the blast furnace. (1mk)

e) State two uses of cast iron. (lmk)

4. a) Below is the diagram of mercury cell used in the electrolysis of brine. Study it and answer the


i) The anode is made of carbon.

Explain why? (lmk)

ii) State another substance that can be used

instead of carbon (lmk)

i) Water is used as a raw material at inlet T;

ii) Explain the function of the water. (lmk)

iv) Identify the by-product at outlet W. (1mk)

v) State one advantage and one disadvantage of using the

mercury cell in the manufacture of sodium hydroxide.

(2mks)

b) A current of 75 Amperes was passed through the cell for

8 hours.

i) Write an equation for the reaction that takes place at the

cathode. (lmk)

ii) Calculate the mass of sodium hydroxide that was

produced, given that 2 moles of sodium amalgam

forms 2 moles of sodium hydroxide. (3mks)

(Na = 23, 0 = 16, H = 1, Faraday = 96,500)

64

5. The grid below represents part of the periodica table. Study it and answer the questions that follow.

The letters do not represent the actual symbols of the elements.

a) i) Give the family to which element J belongs. (lmk)

ii) Select the element which has the largest atomic radius. Explain

iii) Which of the elements G, H, I and J has the smallest atom?

iv) Compare the electrical conductivity of elements I and K. Give a reason (lmk)

v) Write the chemical formula and electron configuration of the ion of H. (lmk)

b) The first and second ionization energies of element K are 590 kJ/mol and 1150kJ/mol respectively.

Explain why the second ionisation energy is greater than the first one. (lmk)

c) The atomic radius of element J is 0.099nm while that of its ion is 0.181 nm.

Explain the difference in the radii. (lmk)

d) Draw a dot (•) and cross (x) diagram to show bonding in the compound formed between element

H and carbon. (lmk)

e) Compare the pH value of the aqueous solution formed when oxides of I and K are dissolved in water.(2mks)

f) Write the equation for the reaction between I and J. (lmk)

6 a) Study the flow chart below and answer the questions that follow.

i) Name reagent R in step Vi (lmk)

ii) State one application of the process in step II (lmk)

iii) Write an equation for the reaction in step III. (lmk)

iv) State one use of polymer W.

b) R - COO- Na+ and R – CH2 OSO3- Na+ represents two types of cleaning agents. Which of the two cleansing

agents would be suitable to use with borehole water containing dissolved calcium chloride? Explain

c) Polysters are polymers joined by an ester link. The polymer below shows a polyster. Study it and answer the


i) Draw the structural formula of the monomers from which it is derived. (2mks)

ii) State the polymerization method by which polyster is made. (lmk)


233/3

CHEMISTRY

PAPER 3 1. You are provided with:

- Solution A, which is 0.1 M sodium hydroxide.

- Solution B, which is 0.02M potassium manganate (VIII).

- Solution C, which is a mixture of sodium oxalate (Na2C2O4) and oxalic acid (H2C2O4) a dibasic acid.

You are required to find the percentage of sodium oxalate in the mixture.

i) Using a pipette and pipette filler, place 25.0cm3 of solution C in to a conical flask.

ii) Fill a burette with solution A and use it to titrate the mixture in a conical flask.

iii) Titrate 25cm3 portion of solution C with 0.lM of solution A using 2-3 drops of phenolphthalein indicator.

iv) Record your results as shown in the table 1 below

You are given that an acidified solution of sodium oxalate reacts in the same way with potassium manganate

(VII) as it does with oxalic acid. Thus:

65

Table I

I II III



Volume of solution A used (cm3)

a) Calculate the average volume of solution A used: (lmk)

b) Calculate the number of moles of:

i) Oxalic acid used to neutralize sodium hydroxide. (lmk)

ii) Concentration of oxalic acid in grams per litter. (H = 1.0, C= 12.0, O = 16.0) (2mks)

Procedure II

i) Use pipette filler to pipette 25cm3 of solution B into a clean dry conical flask.

ii) Heat the contents of the conical flask to about 70°C.

iii) Add 20cm3 of 2M sulphuric (vi) acid and titrate against solution C to a colourless end point.

Repeat the procedure to obtain three concordant readings.

iv) Record your results in the table 2 below.

Table 2

I II III



Volume of solution C used (cm3)

c) Calculate the average volume of solution C used: (lmk)

d) Calculate the number of moles of:

I. Oxalate ions that react with acidified potassium manganate (VII) (2mks)

II. The number of oxalate ions in sodium oxalate in 25cm3 of the mixture. (lmk)

III. Concentration of sodium oxalate in grams per litre. (2mks)

e) Calculate the percentage of sodium oxalate in the mixture. (lmk)


- 2.0g of potassium hydrogen carbonate, solid D.

- 2.0M hydrochloric acid, solution E.

You are required to determine the enthalpy change for the reaction between potassium hydrogen carbonate

and hydrochloric acid.

Procedure

Using a burette place 15.0cm3 of the solution E in a 100cm3 beaker

Measure the temperature of the solution after every half a minute and record the values in table 3 below. At

exactly 2 minutes add all the solid D to the acid and stir the mixture gently with the thermometer. Measure the

temperature of the mixture after every half-minute. Record the values in Table 3 below.

Table 3

Time in minutes 0 ½ 1½ 2 2½ 3 3½ 4 ½

Temperature (oC)

(3mks)

a) Plot a graph of temperature against time. (3mks)

b) Determine from the graph the temperature change T = ___________________ (½mk)

c) Calculate:

I. The moles of potassium hydrogen carbonate used. (H = 1, C = 12, O = 16, K = 39) (lmk)

II. The molar enthalpy of neutralization between potassium hydrogen carbonate and hydrochloric acid.

(Density of water = 1.0 gdm-3, specific heat capacity = 4.2kJkg-1K-l (2mks)

3. a) You are provided with solid F. Carry out the experiment below. Write your observations and

inferences in the spaces provided.

Place all of solid F in a boiling tube. Add about 10cm3 of distilled water and shake until all the solid dissolves,

label the solution F. Use solution F for experiments I to III.

To 2cm3 of solution F, in a test-tube in each of the experiments I, II and III add:

I. Sodium hydroxide drop wise until in excess

Observation Inferences

66

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II. Add 2-3 drops of barium nitrate solution provided followed by 2cm3 of 2M hydrochloric acid to the second

portion. Shake the mixture well.


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III. Add 5 drops of acidified potassium chromate (VI) to third portion.


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b) You are provided with substances G. Carry out the following tests.

Write your observation and inferences in the spaces provided.

i) Place a little of substance G in a metallic spatula and ignite it in a Bunsen burner flame.


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ii) Place about 1 cm3 of G in a test tube. Add a ¼ spatula full of solid H potassium hydrogen carbonate


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iii) To about 2cm3 of substance G, add 2-3 drops of bromine water and warm.


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iv) To about 3cm3 of G in a boiling tube, add acidified potassium chromate (VI) and warm the mixure


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v) Place about 3cm3 of substance G in a boiling tube. Add an equal volume of ethanoic acid, followed by 2-3

drops of concentrated sulphuric VI acid and warm the mixture. Add distilled water.


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UGENYA / UGUNJA DISTRICT JOINT EVALUATION TEST,...

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