kcpe-kcse.com€¦ · Web viewChemistry paper 1, 2&3 (d) What is meant by the word equilibrium(2...

Chemistry paper 1, 2&3 (d) What is meant by the word equilibrium (2 mark)(b) With reasons explain what would happen when(i) Pressure is increased in the system in (a) above (2 marks)(ii) Temperature is increased (2 marks)(iii) Nitrogen (II) Oxide is removed (2 marks)(c) An equilibrium exists between

2NO2(g) N2O4(g)

On the grid below sketch how the concentration of NO2 varies with the reaction path (3 marks)

Concentration of NO3

Reaction path

1. (a) State how burning can be used to distinguish between prepane and propyne. Explain your answer. (3marks) (b) Draw the structural formular of the 4th member of the homologous series in which propyne is a member

(1mark) (c) The flow chart below shows a series of reactions starting withpropan-l-ol. Study it and answer the questions that

follow.

NaOHPropanoic acid

Process Y

Propan -l-ol

ConcentratedH2SO4 Process W

Gas R

High Pressure

Polymer X

(i) Name:

C

Sodalime Heat

Ethane

I. Process Y……………………………………………………….. (1mark)II. Substances R and CIII. Process W……………………………………………… (1mark)IV. Polymer X……………………………………………… (1mark)

(ii) Write a balanced chemical equation for the combustion of propane. (1mark)(iii) State oneuse of polymer X (1mark)

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Chemistry paper 1, 2&3 GITHUNGURI SUB-COUNTY EXAMINATION 233/3 CHEMISTRY FORM FOUR PRACTICAL Paper 3 TIME: 2¼ HOURS

1. You are provided with 10g of solid A which is a mixture of sodium carbonate and sodium chloride. 0.2 M HCl solution B

You are required to

Determine the concentration of sodium carbonate in the mixture. Percentage of sodium chloride in the mixture.

Procedure Transfer the entire solid into a 250 Ml volumetric flask. Add about 100cm3 of distilled water. Shake to dissolve. Top up with more distilled water to make up to the mark. Label this solution A2. Using a pipette and a pipette filler, transfer 25 cm3 of this solution into a conical flask. Repeat the procedure two more times to complete table 1

Table 1 I II III

final burette reading (cm3)initial burette reading(cm3)volume of solution B used (cm)3

(a) Calculate(i) The average volume of solution B used ( 1mark)(ii) The number of moles of HCl in the average titre (1 mark)(b) Write an equation for the reaction ( 1mark)(c) calculate the number of(i) Moles of sodium carbonate in 25cm3 of solution A2 (1 mark)(ii) The moles of sodium carbonate in 250 cm3 of solution A2 ( 1 mark)(d) Determine the mass of sodium carbonate in solid A (1 mark)

(Na=23, C = 12.0, H=1.0 , O= 16)

(e) Calculate the percentage of sodium chloride in solid A ( 1 mark)2. You are provided with Solution D, 2MHCl Solution C 2 M NaOH

You are required to determine the heat of neutralization

Procedure Wrap a plastic beaker with tissue paper and secure it with a rubber band. Use a measuring cylinder to transfer 20cm3 of solution C into a plastic beaker. Take its initial temperature and record it in table 2 below. Using a clean measuring cylinder, measure 5 cm3 of solution B and add it to solution C. Stir the mixture immediately with a thermometer and record the highest temperature in table 2 Continue adding 5 cm3 portions of solution every time record the highest temperature attained to complete the table Table 2

Volume of D add cm3 0 5 10 15 20 25 30Volume of A+D cm3 20 25 30 35 40 45 50Temperature of mixture oC

(4 marks)Plot a graph of volume of solution D (X-axis) against highest temperature (3 marks)

(a) From the graph:(i) Determine the volume of solution D that reacts completely with solution C. (1mark)(ii) The highest temperature change∆ T (1 mark(b) (i) Calculate the amount of heat evolved by the reaction (assume specific heat of capacity =

4.2Jg -1 K-1, density of solution = 1 g/cm3) (1 mark)(ii) Calculate the number of moles of HCl used (1 mark)(iii) Calculate the molar heat of neutralization of HCl (2 marks)

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Chemistry paper 1, 2&3 3. (a) You are provided with solid E. Carry out the following tests and write your observations and inferences in the spaces

provided.(i) Place one third of solid E on a metallic spatula and ignite using a Bunsen burner flame

observation Inferences

( 1 mark) ( 1 mark)

(ii) Place all the remaining solid in a boiling tube. Add 5cm3 of distilled water. Shake to dissolve and divide it into 4portions

(I) to the first portion add three drops of acidified potassium manganate (VII)


( 1 mark) ( 1 mark)

(II) To the second add three drops bromine water.


( 1 mark) ( 1 mark)

(III) To the third portion add all the sodium hydrogen carbonate provided


( 1 mark) ( 1 mark)

(b) You are provided with solid F. Carry out the tests below and record your observations and inferences in the spaces provided.Place all the solid F in a boiling tube. Add 10cm3 of distilled water. Divide into four portions.


( 1 mark) ( 1 mark)

(i) To the first portion, add aqueous hydroxide drop wise until in excess.


( 1 mark) ( 1 mark)

(ii) To the second portion add 5 drops of barium nitrate solution, followed by 3 drops of dilute nitric acid.


( 1 mark) ( 1 mark)

(iii) To the third portion add 3 drops of acidified sodium dichromate (VI) solution


( 1 mark) ( 1 mark)

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Chemistry paper 1, 2&3 GITHUNGURI SUB-COUNTY EXAMINATION 233/1 CHEMISTRY PAPER 1 MARKING SCHEME 2016

1. (a) (i)

(ii)(b) For easier visibility. ¹

2. (a) Mass increases as oxygen combines with copper ¹(b) Mass decreases as ¹ gases escape during decomposition ¹

3. (a) (i) A ½(ii) B ½

(b) A and B¹Lead (II) oxide is amphoteric ¹

4. - Experiment with magnesium ¹- Zinc reacts with oxygen only while ¹- Magnesium reacts with both oxygen and nitrogen. ¹

5. (a) Alkaline earth metals. ¹(b) J does not form compounds as it is chemically stable already. ¹(c) M has a higher melting point than B as it has a stronger metallic bond. ¹

6. (a) 2.8 ¹(b) Na+, O2-, N3-¹

No of protons decrease to the right hence reducing the effective nuclear charge. ¹7. - PCl3 has a simple molecular structure with ½

- Weak van der waals inter-molecular forces ¹- MgCl2 has a giant ionic structure with ½- Strong electrostatic forces between the oppositely-charged ions. ¹

8. (a) Mg(S) + H2O(g) MgO(S) + H2(g) ¹(b) Potassium would react explosively with steam. ¹

9. Graphite has a giant atomic structure hence. ¹high boiling point and is more stable than oil. ¹

10. CaCO3 + 2HCl CaCl2 + H2O + CO2¹Moles of CaCO2 = 15 ½

100Moles of HCl = 2

0 15½

1000 100 0 2

Moles of CO2 produced 0 22

0 1 ¹

Volume of CO2 produced = 0.1 x 24000 ½= 2400cm³½

11. (a) (i) To burn off carbon (II) oxide which is highly poisonous. ¹(ii) H2O(g) + C(S) CO(g) + H2(g) ¹

(b) Potassium hydroxide forms soluble carbonate and hydrogen carbonate. ¹12. Electrons neutrons

O ¹ 1 ¹13. (a) Grey solid ½, Pb2+ ions are discharged as Pb(S) ½

(b) Q = 2.5 x 25 x 60 = 3750C ¹0 36 193000

M 3750 18 5 ¹

14.

15.

Aluminium chloride is hydrolysed ¹ by water to produce H+ ions ¹to produce HCl, a strong acid ¹(a) Ammonium chloride. ¹

3 (b) Alaq 3OH aq AlOH 3 (S)¹(c) Heat ¹

16. - Mobile liquid comprises of S8 molecules ¹- Dark viscous liquid as the S8 chains entangle ¹- The S8 molecules fold into rings which flow independently. ¹

17. (a) - No bleaching. ½- Bleaching ½

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Chemistry paper 1, 2&3

(b) SO2(g) + H2O(l) 2

2 2 H aq SO 3 aq ¹2

SO3 aq Dye SO4aq Bleach ¹18. (a) Sample II ¹

- Requires little soap to lather ¹(b) Temporary hardness removed after boiling. ¹

19. (a) Heat of formation of FeCl3 ¹(b) H3 = H1 + H2 ¹

20. Brown colour would intensify.¹OH- Removed by addition hence ½ backward reaction triggered to replace OH-½

21. (a) I Hydrogen ½II Oxygen ½

(b) Precipitation of PbCl2 prevents flow ¹22. 58n = 116 ½

n = 2 ½ C6H12O2¹

23. (a) When gases react, they do so in simple ratios of volumes and those of their products if gaseous.¹(b) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ½

20 3

100 40 8 cm of O2 ½

Volume of CH 4 82

3 4 cm½

Volume remaining = 40 - 4 = 36cm³ ½24. (a) Alkanols ¹

(b) Oxidation ¹(c) H H

H C C C O H

H H O

40 3925. (a)

19 K has 21 neutrons while K has 20 ¹19

(b) 4 h 2 h 1 2h2 x 1.3 x 109 = 2.6 x 109¹40 40 o

(c) 19 K Ca 1 20

26. (a) Chlorine ¹(b) Increases surface area for dissolving process ¹(c) Cl2¹

27. (a) II(b) Non-biodegradable hence leads to water pollution. ¹(c) (RCOO-)2Mg2+¹

28. - To excess lead (II) carbonate, add nitric (V) acid ¹- Filter to obtain lead (II) nitrate filtrate. ½- Add dil HCl acid. ¹- Filter to obtain lead (II) chloride residue. ½

29. (a) The volume of a fixed mass of a gas is inversely proportional to itspressure at constant temperature. ¹

(b) 60cm³ - 50sec.80cm³ ? 80 50 ¹

t At B

t B

60

M AM B

66 67 64 ¹32

66 67 sec

= 94.28sec ¹

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Chemistry paper 1, 2&3 GITHUNGURI SUB-COUNTY EXAMINATION 233/2 CHEMISTRY PAPER 2 MARKING SCHEME 2016 1. (a) M O2

(b) J and N; Oxides of metals (c) K - has two allotropes (d) giant atomic structure (e) J reacts vigorously while that of N is rapid (f) M, electronic configuration - 2,8,4 cannot lose 4 or gain electrons that is shares (g) 4 L (s) + 5 O2 → 2 L2 O5(s) / 4 P + 5O2 → 2 P2O5

2. (i) 4 O H-(aq) → O2(g) + 2H2O(l) + 4 e(ii) Hydrogen; volume is twice that at X.(b)(i) 0.22 = 0.0012

184(ii) Q = 0.06 x 99 x 60

= 356.4 C.0.22 → 356.4184 → 356.4 x 184

0.22= 65577.6 C.

96500C → IF65577.6C → 1 x 65577.6

96500= 3 F.3 moles of electrons.

(iii) Gn+ = +3(c)(i) A(s) /A2+(aq) // C+(aq) / C(s)

(ii) Electroplating3. (a) the heat change in converting reactants to product is regardless of the

route followed.(b) 2C(s) + H2(g) → C2H2(g)

+O2 +1/2 O2 + 3 /2 O2

CO2(g) + H2O(g)

(c) Heat of formation of ethyne (d) +227 = 2 x -394 + -286 - ∆Hc

∆Hccomb = 2 x - 394 -286 -227 = - 1301 kJ/mol.

(e) - Availability- Cheap - Environmental friendly - High energy

4. (a) to dry the biogas(b) P - water

Y - CO2

(c) - black substance turns brown- colourless liquid formed on cooler parts of tube X

(d) (i) Reduction(ii) 4Cu O(s) + CH4(g) → 4Cu(s) +CO2(g) + 2H2O(l)

(e) Carbon, Hydrogen (f) - to allow product P to condense

- Also for product Y to be collected by syringe.5. a) (i) Chlorine gas reacts with steel hence corroding it.

(i) use of steel diaphragm prevents to prevent the mixing of the two.(ii) i) anode - 2CL⁻(l) → Cl2(g) + 2e⁻

ii) Cathode - Na+(l) + e⁻+ Hg(s) → Hg/Na(l)

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Chemistry paper 1, 2&3 b) (i) to lower m.p of NaCl thus reducing the cost of production. (ii) fractional distillation of liquidified metal c) H+ ions are lower than Na+ ions in the electro chemical series Hence H+ ions would be discharged instead of N. b) (i) 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)

(ii) i) sodium is less dense than water ii) sodium hydroxide solution formed is alkaline.

(i) Equilibrium is the state of balance where the rate of forward and rate of backward reaction is the same. (b) (i) No change, reactant and product side have equal volume 2,2.

(ii) Equilibrium shifts to the left; reaction is endothermic. (iii) Equilibrium shifts to the right, le‟charteliers principle removal of product.

(c)

Con of No2

Reaction Path 7. (a) When ignited propane burns with a blue flame because it is a saturated hydrocarbon (alkane) while propyne

burns with a yellow smoky flame because it is an unsaturated hydrocabon √ (alkyne) H H H

| | |(b) H - CC- C - C- C -H

| | |H H H

(c) I oxidation II R - Propene ( Prop - l-ene) C- Sodium propnoate

III Dehydration IV polypropene

(ii) C3H8 +5O2(g) → 3CO2(g) + 4H2O(l)

(iii) Used to manufacture (i) plastic ropes(ii) plastic crate(iii)Plastic chairs

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Chemistry paper 1, 2&3 GITHUNGURI SUB-COUNTY EXAMINATION 233/3 CHEMISTRY PAPER 3 MARKING SCHEME 2016

1. Table 1…………………………………………………………………………………….. (5 marks)Distributed as follows:A. Complete table………………………………………………………………………… (1 mark)

Conditions:-i) Complete table with 3 titrations done (1 mark)ii) incomplete table with 2 titrations done ( ½ mark)iii) incomplete table with 1 titration done ( 0 mark)

Penaltiesi) wrong arithmetic/subtractionii) inverted tableiii) burette reading >50unless explained (50+)iv) unrealistic values i.e values less than 1cm3 or in hundredsNB: penalize ½ mark once for one for all

B Use of decimals (tied to the 1st and 2nd row only…………………………………… (1 mark)i) Accept 1 or 2 decimal places used consistently otherwise penalize fullyii) If 2 decimal places are used the 2nd must be a 0 or a 5 otherwise penalize fullyiii) Accept inconsistency in the use of zero‟s e.g. 0, 0.0, and 0.00

C Accuracy…………………………………………………………………………… (1 mark)Compare the candidate‟s correct titre with the teacher‟s valueConditions;-i) If at least one titre value is within 0.1 of teachers value award (1 mark)ii) If no value is within 0.1 of the teacher‟s value but there is one within 0.2 award (½ mark)iii) If no value within 0.2 award... (0 mark)NB: where the candidate has wrong arithmetic use the correct worked out value to award.

D. Principles of averaging……………………………………………………………... (1 mark)Values to be averaged must be within 0.2 of one anotheri) If three consistent titres are done and averaged (1 mark)ii) If three titrations are done but only two are consistent and are averaged (1 mark)iii) If only two consistent titrations are done and averaged (1 mark)iv) If three inconsistent done and averaged (0 mark)v) If three consistent titrations done,. two averaged (0mark)vi) If two inconsistent done and averaged (0mark)Penalties Penalize ½ mark for i) No working if answer is correct ii) Rounding off to 1 decimal place (unless it works out to 1 decimal place or to whole number)

E Final accuracy (1 mark)Compare the candidate‟s correct average titre with the teacher‟s valuei) If within 0.1 (1 mark)ii) If within 0.2 (½ mark)iii) If not within 0.2 (0 mark)NB: where there are two possible average values use the value giving maximum credit Calculations ii) Moles HCl

0.2 x titre½ 1000 = correct ans. accept answer to at least 4 decimal places(Unless it (1mark)

works out otherwise)½- ignore units, but if given must be correct- Penalize wrong transfer of titre value(b) Equation for the reaction

Na2CO3(aq) + 2HCl(aq) → 2NaCl(aq) + CO2(g) + H2O(l) (1 mark)Penalize ½ mark for wrong or omitted state symbols

(c) (i) Moles Na2CO3in 25 cm3

0.5 x answer (a)(ii) ½= correct answer½ (1 mark)

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Chemistry paper 1, 2&3 (ii) Moles Na2CO3 in 250cm3

25 x answer c(i)½ = correct answer½ (1 mark)250

(d) Mass of sodium carbonate in solid A 106 x answer c(ii) above½ = correct answer½ correct units (1 mark)

(e) Percentage of sodium chloride(10 - answer d above)½

10 x 100 = correct answer½ (1 mark)Penalize for answer if above 40% or below 20%

2 Table 2 …………………………………………………………………………….. (4 marks)A. Complete table ………………………………………………………………… (1 mark)

6-7 entries (1mark)4-5 entries (½ mark)

B. Decimal place - accept whole numbers or 1 decimal place, which must be a zero or a fiveC. Accuracy - compare with teachers value , 2o (1 mark)D. Trend - continuous rise ½ mark followed by a fall ½ mark (1 mark)

Graph (3 marks)- Labelling of axes ½ mark- scale ½ mark- more than- Plots 1 mark ½ of grid- shape 1 mark(a)(i) Volume of solution D

- showing ½ mark - correct reading ½ mark

(ii) ∆ T………………………………………………………………………………………….1 mark) - Showing on correct extrapolated graph ½ mark - Correct reading ½ mark

(b) (i) MC∆T……………………………………………………………………………….(1 mark)- correct substitution ½ mark- correct answer ½ mark

(ii) Moles HCl volume in a(i) x 2 M ½ = correct answer ½ mark

1000 (iii) Molar heat of neutralization Hcl…………………………………………………..(2 marks)

Ans b)(i)1 Ans b(ii)

∆ H = -correct answer kJ mol-1

Penalize - ½ mark if -ve sign is missing- ½ mark if units missing or wrong

3. (a) You are provided with solid E. Carry out the following tests and write your observationsand inferences in the spaces provided.

(i) Place one third of solid E on a metallic spatula and ignite using a Bunsen burner flame

observation InferencesBurns with a yellow sooty /smoky flame Long chain hydrocarbon or unsaturated organic

compound, or compound with a high carbon hydrogen ratio Or

C = c -c ≡ c-

(1 mark) Reject - long chain hydrocarbon (1 mark)

(ii) Place all the remaining solid in a boiling tube. Add 5cm3 of distilled water. Shake to dissolve and divide it into4 portions

(I) to the first portion three drops of acidified potassium manganate (VII)

Observation InferencesKMnO4 decolourised R - OHAcceptPotassium Manganate (VII) turns from C= c or -C ≡c - presentpurple to colourless

1 mark 1 mark

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Chemistry paper 1, 2&3 (IV) To the second a three drops bromine water.

Observation InferencesBromine water decolourised 1(Accept Orange/yellow/red bromine turnscolourless) C = C

( 1mark) OrC ≡ c (1 mark)

(V) To the third portion all the sodium hydrogen carbonateObservation inferenceseffervescence/bubble H+/ R - COOH1

Accept carboxylic acid for ½ mark(1 mark) ( 1 mark)

(c) You are provided with solid F. Carry out the tests below and record your observations and inferences in the spacesprovided. Place all the solid F in a boiling tube. Add 10cm3 of distilled water. Divide into four portions.observation inferencesSolid dissolves to form a colourless Absence of coloured ions e.g. Cu2+, Fe2+ Fe3+ ½solution½ mark mark

(i) To the first portion, add aqueous hydroxide drop wise until in excess.

observation InferencesNo white ppt formed, even in excess Zn2+, Al3+, Pb2+, Mg2+. Ca2+ absent

Any 3 ions1(1 mark) Only 2 ion

Reject Ba2+ absent (1 mark)

(ii) To the second portion add 5 drops of barium nitrate, followed by 3 drops of dilute nitric(V) acid

Observation inferencesWhite ppt ½ formed. CO32-½ or SO32- ½ presentPpt dissolves on ½ addition of nitric (v) (1 mark)acid (1 mark)

iii) To the third portion add 3 drops of acidified sodium dichromate (VI) solutionObservation inferencesK2Cr2O7 changes1 from orange to green SO32- 1 present(1 mark) (1 mark)

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Chemistry paper 1, 2&3 MURANG’A SOUTH SUB-COUNTY MULTILATERAL EXAMINATION 2016 Kenya National Examination Council

233/1 CHEMISTRY PAPER 1 (THEORY) TIME: 2 HOURS JULY/AUGUST 2016

1. a) Three isotopes of Magnesium has mass numbers 24, 25 and 26. What is the mass number of the most abundant isotope ofMagnesium? Explain. (2mks)b) Define the term isotope. (1mk)

2. a) Define hard water. (1mk)b) The structure below represents two cleansing agents.

Which of the above cleansing agent would be suitable for washing in hard water? Give a reason. (2mks)3. The heat of neutralization of a strong acid is usually 57.4kJmol-1, whereas that of a weak acid is less than 57.4kJmol-1 .

Explain (2mks)4. When an electric current of 0.5A was passed through a molten chloride of J for 32 minutes and 10 seconds, a mass of 0.44g of

J was deposited at cathode.1F = 96500Ca) Calculate the quantity of electricity used. (1mk)b) Determine the value of x if the ion of metal J is represented as Jx+ (2mks)

5. Your friend‟s clothes have caught fire. Inorder to extinguish the fire you decide to cover with a damp blanket. What is thepurpose of the clamp blanket? (1mk)

6. Calculate the number of Calcium atoms in 10g of calcium.(Ca = 40, Avogadro number = 6.0 x 1023) (1mk)

7. The table below shows the pH values of some solutions.Solution J K L M NpH 6 13 2 10 7

a) Which solution is likely to be:i) Potassium hydroxide (1mk)ii) Lemon juice (1mk)b) Explain why a solution of hydrogen chloride gas in methyl benzene was identified as N. (1mk)

8. A piece of burning magnesium ribbon was placed in a gas jar full of nitrogen gas. The product Q formed was then reactedwith water.a) Write the chemical formula for the product Q. (1mk)b) Write the equation for the reaction between product Q and water. (1mk)c) Using dot (•) and cross (X) diagrams to represent electrons, draw the structure to show bonding in a nitrogen

molecule. (N = 14) (1mk)9. How would the following pair of compounds be chemically distinguished? CH3COOH and CH3CH2OH. (2mks)10. Name the products of electrolysis of fused copper (II) chloride using carbon electrodes.

Anode ( ½ mk)Cathode ( ½ mk)Explain (1mk)

11. Zinc metal can be used in the laboratory to prepare hydrogen gas from an appropriate mineral acid while copper metal cannot.Explain. (1mk)

12. a) State one factor that can determine stability of an atom. (1mk)b) Radioactive polonium -216 decays as shown below.

Find the value of M and N. (2mks)c) If after 112 days 1/16 of Polonium remained, calculate the half-life of polonium. (2mks)

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Chemistry paper 1, 2&3 13. When bromine gas reacts with aqueous sodium hydroxide an equilibrium is established as shown below.

Br2(aq) + 2OH-(aq) Br-(aq) + OBr-(aq) + H2O(l)(Brown) Colourless

What observation would be made if a few drops of dilute sulphuric (VI) acid were added to the equilibrium mixture? Explain. (2mks)

14. One compute combustion of 0.5g of an organic compound P (containing only carbon, hydrogen and oxygen) 0.733g of carbon (IV) oxide and 0.3g of water were produced. Determine the empirical formula of P. (3mks)

15. Compare the atomic sizes of sodium and magnesium. Explain. (2mks)16.

a) Name gas X. (½ mark)b) Write an equation for production of gas x in the set-up. (1mk)c) It‟s hat to test whether gas x supports burning using a glowing splint. Explain. (2mks)

17. When solid M is dissolved in water, it dissolves to form a blue solution. Addition of ammonia solution forms a blueprecipitate which dissolves in excess to form a deep blue solution. Write the formula and name of the ion responsible for thedeep blue solution. (2mks)

18. The diagram below represents the structure of aluminium chloride.a) Identify the bonds labelledM (½ mark)N (½ mark)b) What is the difference between bonds M and N? (1mk)

19. a) Define hydration energy. (1mk)b) Given that hydration energies of Ca2+ and Cl- are -1891kJmol-1 and - 384kJmol-1 respectively and that the lattice energyof calcium chloride is +2237kJmol-1, calculate the molar enthalpy change of solution of calcium chloride. (3mks)

20. The diagram below shows an experiment involving chlorine water.

a) State and explain the observations made after 24 hours. (2mks)b) Write an equation to show the formation of gas A. (1mk)c) State one use of chlorine gas. (1mk)

Page | 252


21. The solubility of salt Y at 600C is 40g/100g of water and 48/100g of water at 1000C.a) How much salt Y would saturate 190g of water at 1000C. (1½ mark)b) 150g of a saturated solution of Y is 1000C is cooled to 600C. Calculate the mass of Y that crystallizes. (1 ½ mks)

22. The diagram below shows the appearance of two pieces of paper placed in different parts of a non-luminous flame of aBunsen burner and removed quickly before they caught fire.

a) What do the experiments show about the outer region of the flame? (1mk)b) From the above experiment, which part of the flame is better for use in heating? Give a reason. (2mks)

23. Steam is passed over heated magnesium as shown in the diagram below.

a) State one observations that will be made in the tube as heating is carried out. (1mk)b) What substance is being burnt at A? (1mk)c) Write a balanced chemical equation to show the reaction which takes place in the combustion tube. (1mk)

24. The volume of a given mass of a gas is 250cm3 at 270C and 720mmHg pressure. What will be the volume of the gas at s.t.p.(3mks)

25. Given the equation N2(g) + 3H2(g) 2NH3(g) DH= -92kJmol-1Explain what happens to the position of the equilibrium whena) Temperature is raised. (1mk)b) Pressure is changed. (2mks)

26. State and explain the observations made when a few drops of concentrated sulphuric (IV) acid is added toa) Hydrated Copper (II) sulphate. (2mks)b) Sugar (2mks)

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

a) Given that solid N burns in air with a red flame. Identify:-i) Cation present in solid N (½ mark)ii) Metal oxide L (½ mark)iii) Gas X (½ mark)b) Write down the formula of the anion present in solid N. (½ mark)

28. Determine the volume of 2.0M NaOH which when diluted to 250cm3 would produce a 0.8M NaOH solution. (2mks)29. Explain how you would obtain pure ammonium chloride from a mixture of lead sulphate and ammonium chloride? (2mks)30. a) Carbon exhibits allotropy. Name one element other than carbon that has the same characteristic. (1mk)

b) In terms of structure explain why graphite conducts electricity while diamond does not? (2mks)c) Define allotropy. (½ mark)

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233/2 CHEMISTRY PAPER 1 (THEORY) TIME: 2 HOURS

1. Study the periodic table below and answer the questions that follow. The letters do not represent the actual symbols of the elements.

a) Name the chemical family to which the following elements belongi) C, G, O (½ mk)ii) B, F, N, S (½ mk)b) Classify elements H and M as either metals or non-metals.

H - (½ mk)M - (½ mk)

c) State one use of element.A (1mk)N - (1mk)

d) Compare the atomic radius of G and H. (2mks)e) Ionic radius of R is larger than its atomic radius. Explain. (2mks)f) Write down the formula of the compound formed when element I reacts with element X. (1mk)g) Identify the strongest oxidising agent. Explain. (2mks)h) Write down the electron arrangement of:-

i) Element P (½ mk)ii) Ion of E

i) Identify an element with a charge of +2. (½ mk)j) Compare the first and second ionisation energies of element H. (2mks)

2. i) Define a binary electrolyte. (1mk)ii) The following are half-cell equations for some elements. The letters do not represent the actual symbols. Use the

information to answer the questions that follow.EOV

M2+(aq) + 2e- → M(s) +0.34

L2+(aq)+ 2e- → L(s) +0.84

K2+(aq) + 2e- → K(s) -0.13

J2+(aq) + 2e- → J(s) -0.76

2V+(aq) + 2e- → V2(g) 0.000

a) Write down the E0 value of the strongest reducing agent. (1mk)b) Select two half-cells that would produce the highest emf of a cell. (1mk)c) Calculate the emf of the cell in (b) above. (1mk)d) Give the cell diagram notation for the cell in (c) above. (1mk)e) What is element V? Explain. (2mks)f) State two functions of a salt bridge. (2mks)

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Chemistry paper 1, 2&3 3. Use the flow chart below to answer the questions that follow.

a) Identify the substance labelledX - (1mk)Y - (1mk)

b) Name two substances being recycled in the process represented by the flow chart. (2mks)c) Name the process that take place in

S- (1mk)R - (1mk)

d) Give one uses of calcium chloride. (1mk)e) Write down balanced chemical equations for the reactions that takes place in chambers

Q - (1mk)T - (1mk)

f) Using ionic equations, explain how sodium carbonate can be used to soften hard water. (2mks)g) Other than softening of hard water, give one other use of sodium carbonate. (1mk)

4. The flow chart below shows some chemical reactions.i) Use it to answer the questions that follow.

a) Write the name and formula of the organic compounds P, V and Wi) Name P (½ mk)

Formula (½ mk)ii) Name V (½ mk)

Formula (½ mk)iii) Name W (½ mk)

Formula (½ mk)

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Chemistry paper 1, 2&3 b) Write the name of the process that leads to the formation of substance (s) V, T, P (½ mk)c) Give one necessary condition for the formation of compound P. (1mk)d) If the relative molecular mass of compound U is 84,000 units, determine the value of n.

C = 12 O = 1.0 (2mks)e) Write the equation for the reaction leading to the formation of substance S. (1mk)f) State and explain the observation made when substance W and C2H4 are burnt in excess air. (2mks)g) Explain why an organic compound with formula C3H6 burns with a more sooty flame than C3H8. (2mks)

5. Nitrogen gas can be obtained from air as shown below.

a) What is the purpose of the followingi) Potassium hydroxide solution? (1mk)ii) Copper turnings?

(1mk)b) Why should water be pumped into the aspirator? (1mk)c) Name another substance that can be used in place of potassium hydroxide. (1mk)d) The nitrogen gas obtained above is not pure. Identify one gaseous impurity in the gas. (1mk)e) The flow chart below shows how pure nitrogen gas is obtained.

i) What is the functions of the following chambers?Filter (1mk)Chamber X (1mk)

ii) Name the process that takes place in chamber Y. (1mk)iii) Identify

M - (½ mk))N (½ mk)

g) State two uses of nitrogen gas. (2mks)

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Chemistry paper 1, 2&3 6. The diagram below shows the extraction of sulphur.

a) i) What name is given to the process above. (1mk)ii) State the uses of the pipesA (1mk)B (1mk)C (1mk)

b) Give two crystalline allotropes of sulphur. (1mk)c) Write an equation for the combustion of sulphur. (1mk)d) Name the product formed when a mixture of sulphur and iron dust is heated. (1mk)e) Give two uses of sulphur. (2mks)f) 6.0dm3 of sulphur (IV) oxide were oxidised by oxygen to sulphur (VI) oxide. (2mks)

Write the equation for the reaction. (1mk)7. 0.6g of Manganese (IV) oxide was placed in a flask and 25cm3 of hydrogen peroxide added. The volume of oxygen gas

produced was recorded after every 10 seconds. The results obtained were recorded in the table below.

a) Plot a graph of volume (cm3) against time (sec). (3mks)b) From the graph, determine the volume of oxygen gas produced. (1mk)c) The experiment was repeated using more concentrated hydrogen peroxide.

On the same axis; sketch the curve that was obtained. (2mks)d) Write an equation for catalytic decomposition of hydrogen peroxide. (1mk)e) Give the test for oxygen gas. (1 mk)f) State two uses of oxygen gas. (2 mk)

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233/3 CHEMISTRY PAPER 3 (practical) TIME: 2 HOURS

Confidential

1. Solution A, 60cm3 of 2.5M HCl2. Solution B, 100cm3 of 0.05M NaOH3. Solution C, 10cm magnesium ribbon4. 10ml measuring cylinder5. 25ml pipette6. 50ml burette7. Complete stand8. Stop watch9. 2 labels10. Distilled water11. 6 test-tubes12. 0.5g sodium hydrogen carbonate

13. 5cm3 ethanol14. 1-14 pH chart15. Solid R, 1g Oxalic acid16. Solid Q, Mixture of (NH

4)2SO4 and Al2(SO4)3 ratio 1 : 117. Pipette filler18. Phenolphthalein indicator19. 250ml conical flasks - 220. 250ml volumetric flask21. 1 - boiling tube22. 1 Spatula

ACCESS TO: 23. Universal indicator solution 24. Acidified Potassium Manganate (VII) solution 25. Bromine water 26. Conc. Sulphuric (VI) acid 27. Means of heating 28. 2M lead (II) nitrate solution29. 2M dilute nitric (V) acid solution30. 0.5M Barium nitrate solution31. 2M sodium hydroxide solution32. 2M Aqueous ammonia33. 2M hydrochloric acid

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233/3 CHEMISTRY PAPER 3 (practical) TIME: 2 HOURS

1. You are provided with • Solution A, dilute hydrochloric acid • Solution B, made by dissolving 0.5g of sodium hydroxide in water and made up to 250cm3 of solution • Solid C, magnesium ribbon • Phenolphthalein indicator

Your are required to: i) Standardise solution A.ii) Determine the rate of reaction between solution A and magnesium

PROCEDURE 1i) Measure exactly 10cm3 of solution A using a burette and transfer into a 250ml volumetric flask. Top up to the mark using

distilled water. Label this solution D.ii) Drain the remaining solution A in the burette, rinse the burette thoroughly and fill it with solution D. iii) Pipette 25cm3 of solution B into a conical flask. Add three drops of Phenolphthalein indicator. iv) Titrate solution D with solution B. Record your results in the table below. Repeat the procedures (iii) to (iv) to complete the

table.

(4mks) (a) Calculate the average volume used. (1mk)(b) i) Calculate number of moles of solution B used. (1mk)

ii) Number of moles of solution D in 250cm3 of solution. (1mk)iii) Molarity of solution A. (1mk)

PROCEDURE II i) Cut solid C into equal parts each 2cm. ii) Using a burette, measure 12cm3 of solution A, into a clean boiling tube. iii) Drop one piece of solid C into the boiling tube containing solution A and start the stop watch immediately. Stop the

stopwatch when all solid C has just reacted. Record your results in the table below.

v) Repeat steps (ii) and (iii) above using 10cm3, 8cm3, 60cm3 and 4cm3 of solution A. Top up each with distilled water to make 12cm3 of solution and complete the table below.

(6mks)

a) Plot of a graph of 1/t (y-axis) against the concentration of solution A. (3mks)b) From the graph, determine the time taken for the reaction to reach completion when 1.5 moles of solution A are used.

(2mks)c) Comment on the shape of the graph. (1mk)

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2. You are provided with solid Q. Carry out the tests below and record your observations and inferences in the spaces provided.a) Strongly heat a spatula-end full of solid Q in a dry test tube.

Observation Inference(½ mk) (1mk)

b) i) Place the remaining solid Q in a boiling tube. Add 10cm3 of distilled water. Divide the solution into five portions.Observation Inference(½ mk) (½ mk)

ii) To the first portion, add aqueous lead (II) nitrate solution.Observation Inference(½ mk) (½ mk)

iii) To the second portion add dilute nitric (V) acid, followed by barium nitrate solution.Observation Inference(½ mk) (½ mk)

iv) To the third portion add a few drops of sodium hydroxide until in excess.Observation Inference(1mk) (1mk)

v) To the forth portion add few drops of aqueous ammonia until in excess.Observation Inference(1mk) (½ mk)

vi) To the fifth portion add a few drops of hydrochloric acid. Warm the contents.Observation Inference(1mk) (½ mk)

3. Your are provided with solid R. Carry out the tests below and record your observations and inferences.a) Place a spatula-end full of solid R in a dry boiling tube and add about 10cm3 of distilled water. Shake thoroughly and

heat to boil.Divide the solution into five portions.Observation Inference(1mk) (½ mk)

b) i) Test the first portion with the universal indicator solution provided.Observation Inference( ½ mk) (1mk)

ii) To the second portion add a few drops of acidified potassium manganate (VII) solutionObservation Inference(1mk) (1mk)

iii) To the third portion add a few drops of bromine water.Observation Inference(1mk) (1mk)iv) To the forth portion, add half spatula of sodium hydrogen carbonate.Observation Inference(½ mk) (½ mk)

v) To the fifth portion, in a boiling tube, add 5cm3 of ethanol followed by a few drops of concentrated sulphuric (VI) acid.Warm the mixture.Observation Inference(1mk) (½ mk)

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233/1 CHEMISTRY PAPER 1 (THEORY) TIME: 2 HOURS Marking scheme

1. a) The ore of atomic number 24 (1mk). Because it is closer to R.A.M (24.3) that means it contributes to R.A.M more than theother two.b) Atoms of the same element with the same number of protons but different number of neutrons. (1mk)

2. a) Water that does not lather easily with soap. (1mk)b) A (1mk) - does not form scum with hard water (1mk)

3. Weak acid is slightly ionised.(1mk) Some heat is absorbed during ionisation of an unionised acid. (1mk)4. a) Q = It

= 0.5 x 1930sec = 965C

b) Jx+(l) + Xe- →J(s) 44g

965C → 0.44g ? 44g

= 44 x 965 1/2 = 96500C

0.44x x 96500 = 96500 x = 1

96500 96500 charge = 1+

5. To cut the supply of oxygen gas.6. 40g contains 6.02 x 1023 Arogadros number

10g ?= 1.505 x 1023 atoms.

7. a) i) K ( 1mk)ii) J (1mk)b) Hydrogen chloride gas in methyl benzene, does not ionise to form an acidic solution. (1mk)

8. a) Mg2N2 (1mk)b) Mg3N2(s) + 6H2O(l) → 3Mg(OH)(aq) + 2NH3(g) (1mk)

c)

9. Ethanoic acid (CH3COOH) reacts with sodium carbonate to liberate carbon (IV) oxide while ethanol (CH3CH2OH) doesnot. (1mk)

10. - Copper metal Copper chloride when fused- Chloride gas (molten) in a binary electrolyte.

11. Copper metal is below hydrogen in the reactivity series hence it cannot displace hydrogen from acids. (1mk)12. a) The ration protons to neutrons in the nucleus of an atom. 1mk

(b) 216 = 208 + 4m + 0 84 = 82 + 2m - n but m = 24m = 8 :. 82 + 4m = 2 = 84 = 86 - n

-n = -2n n = 2

c)

4 half-lifes = 112 days 1 half life ??

1 x 112 = 28 days (1/2mk)4

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Chemistry paper 1, 2&3 13. Brown colour would intensity (1mk)

OH- removed by addition hence backward reaction triggered to replace OH-14. Since 12g of carbon are present in 1 mol = (449) CO2

Mass of carbon in 0.733g CO2 = 12 x 0.733g44

= 0.1999g = Mass of carbon in P

Since 2g of hydrogen are present in 1mol (=18g) H 2O

Mass of hydrogen in 0.300g of H2O = 2 x 0.300g18

= 0.333g = Mass of hydrogen in P

Hence mass of oxygen in P = 0.5 - 0.1999 = 0.0333 = 0.2668g (1/2mk)

Atoms C H OMass 0.1999 0.0333 0.2668Moles 0.1999 0.0333 0.2668

12 1 16

0.01666 0.0330 0.016680.01666 0.01666 0.01666

1 : 2 : 1Hence empirical formula CH2O

15. Sodium has a bigger atomic size than magnesium 1mk. Atomic radius decreases across period because of the increase inthe nuclear charge

16. a) NOb) 8HNO3(aq) + 3Cu(s) → 3Cu(NO3)(aq) + 2NO(g) + H2O(l) 1mkc) Readly combines with oxygen to form nitrog en (IV) oxide. (1mk) Because it is higly unstable. (1mk)

17. [Cu(NH3)4]2+ Tetra ammine copper (II) ions.)18. a) M - Covalent bond

N - dative bond b) For M, shared electrons are coming from the species. For N, shared electrons are contributed by one species.

19. a) This is the energy change that occurs when one mole of gaseous ions become hydrated. (1mk) b) Hsol = Lattice energy + Hydrated energy

= -2273 + (-1891) + 2(-384) = -422kJ/mol

20. a) Chlorine water changes colour from yellow to colourless. (1mk)- Chlorine water decomposes to form hydrochloric acid and oxygen.

b) 2HOCl(aq) → 2HCl(aq) + O2(g) 1mkc) - Bleaching agent,

- Treatment of water. Any ( 1mk)21. a) 48 100g of H2O

190g of H2O190 x 48 = 91.2g100

b) 150 - 100 = 50 - 40 = 10g of crystals22. a) It is the hottest part.

b) The outermost regionCO2 - There is enough oxygen to ensure complete combustion.

23. a) A white solid is formed. 1mkb) Hydrogen gas. 1mkv) Mg(s) + H2O(g) → MgO(s) + H2(g) (1mk)

24. P1V1 = P2 V2 V1 = 250cm3 V2 = ?

T1 T2 P1 = 720mmHg P2 = 760mmT1 = 270 + 273 = 300K T2 = 273K

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70 x 250 = 760 x V2 760 x 300 = 720 x 250 x 273300 273 760 x 300 760 x 300

V2 = 215.53cm325. a) Increase in temperature fovours the backward reaction. i.e. the equilibrium shifts to the left. Backward reaction is

Endothermic.b) Equilibrium will shift to the left when the pressure is decreased and to the right when the pressure is increased.Increase in pressure favours the side with few molecules and vise versa. (1mk)

26. a) Turns white (1mk) Removal of water crystallisation to form white anhydrous copper (II) sulphate (1mk)b) The sugar crystallize change to black. (1mk)This is after removal of molecules of water.

H2SO4C6H12O6 → 6C + H2O (1mk)

27. a) i) Ca2+ or calcium ionsii) CaO or calcium oxideiii) NO2 or Nitrogen (IV) oxide

b) NO3- or Nitrate ion

28. M1V1 = M2V20.4

2 x V1 = 250 x 0.8 (1mk) = 100cm3 (1mk)

2 2

29. Place the mixture into a beaker and cover with a watch glass containing cold water. (1mk)Heat the mixture gently Ammonium chloride will sublime, to give ammonia and hydrogen chloride that later recombineto form ammonium chloride.

30. a) Sulphur (1mk)b) Presence of delocalised electrons (1mk) in graphite that are absent in diamond. NB: Explanation should touch onstructure and bonding. (1mk)c) Existence of an element in more than one form in the same physical state,

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233/2 CHEMISTRY PAPER 2 (THEORY) TIME: 2 HOURS Marking scheme

1. a) i) Alkali metals (½ mark)ii) Noble gases (½ mark)

b) H - Metals (½ mark)M - Non metals (½ mark)

c) A - Air balloons ( 1mk)N - Prevention of oxidation of filament. (1mk)

T - Substitution (Chlorination)P - Esterification

c) Conc H 2SO4d) 28n = 84000

n = 3000e) 2CH

d) G has a bigger atomic radius than H (1mk). Thereis an increase in nuclear chargee) R forms an ion by gaining an electron.

The negative charge is bigger (1mk) than thepositive.

f) I2X3 (1mk)

g) E (1mk). It has the biggest E0 value / Has hightendency to gain electrons.

h) i) P - 2 .8.8.2 (½ mark)ii) Ion of E ==> 2.8 (½ mark)

3CH2OH(l) + 2Na(s)→2CH3CH2ONa(s)f) W burns with a blue flame. 1mk

C 2H4 burns with a yellow sooty flame. (1mk)

g) The hydrogen carbon ratio in C 3H8 if bigger than

C 3H6 3 : 8 and 1 : 2

5. a) i) To remove carbon (IV) oxide 1mkii) To react with oxygen 1mk

b) The drive out air 1mkc) Concentrated sodium hydroxide 1mk d) Argon

i) H or P (½ mark)j) The second ionization energy of H is bigger than

the 1st (1mk). 2nd ionisation energy involves theremoval of an electron from charged particle.

2. i) An electrolyte with only two types of ions. (1mk)ii) a) -0.76V (1mk)

b) L2+(aq) & J2+(aq) (1mk)

c) +0.84 - -0.76 = +1.6V 1mk

d) J (s) / J2+(aq) // L2+(aq) / L(s)

e) Hydrogen, 1mk Has an E0 value of 0.00V, used asthe standard electrode potential. (1mk)

d) i) Complete the circuit by making contractbetween the two solutions (electrolyte). (1mk)

ii) Maintain balance of charges in the electrolyte.

3. a) X - CO 2

e) i) Filter to remove dust particles throughelectrostatic precipitation.Chamber X - To remove moisture / dry the gas

ii) Fractional distillation 1mkiii) M - Oxygen (½ mark)

N - Argon (½ mark)f) Manufacture of ammonia ( 1mk)- As a refrigerant for semen ( 1mk)- In light bulbs to prevent oxidation of the filament

6. a) i) Frasch Process (1mk)ii) A - Takes in hot compressed air to force. out the molten

sulphur to the surface ( 1mk)B - Takes out molten sulphur 1mkC - Takes in superheated water to melt the sulphur

b) - Rhombic sulphur (½ mark)- Monoclinic sulphur (½ mark)

c) S SO 1mkY - Ca(OH) 2

b) Carbon (IV) oxideAmmonia

c) S - DecompositionR - Filtration

d) Drying agente) Q

H 2O(l) + NH3(g) + NaCl(aq) + CO2(g)

→NH 4Cl(aq) + NaHCO3(s)

TCa(OH) 2 (aq) + 2NH4Cl(aq) → CaCl(aq) +

2NH

(s) + O2(g) → 2(g)d) Iron (II) Sulphide 1mke) It is used in the vulcanization of rubber 1mk- It is used in manufacture of matches and fireworks1mk- Manufacturer of sulphuric acidf) i) 2SO 2(g) +O2(g) → 2SO 3(g) 1mk

7. a) Scale (½ mark)Labelled (½ mark)Plotting 1mkShape 1mk (smooth curve)

b) 55cm3 (MUST be shown on the graph) 1mk(Otherwise penalise fully)

3(g) + 2H2O(l)f) Ca2+(aq) + CO32-(aq) → CaCO 3(s)

Mg2+(aq) + CO32-(aq) → MgCO 3(s)g) Making glass

4. a) i) CH 3COOCH2CH3 → Ethylethanoateii) 1, 2 - dibromoethane CH 2BrCH2Briii) Ethane CH 3CH3

b) V - Addition (bromination)

c) Curve more steep and above the previous curveNB - Flatten at the same point 1mk

MnO 2d) 2H 2O2(l) → O 2(g) + 2H2O(l) 1mke) Relights a glowing splint 1mkf) In hospitals to patients with breathing problems 1mk- Oxyacetylene flames in welding 1mk- Mountain climbers and deep sea divers.

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Chemistry paper 1, 2&3 MURANG’A SOUTH SUB-COUNTY MULTILATERAL EXAMINATION 2016 Kenya National Examination Council 233/3 CHEMISTRY PAPER 3 (practical) TIME: 2 HOURS Marking scheme

Marks distributed as follows a) Complete table (1mk) 3 titrations done (1mk) Incomplete table with 2 titrations ( ½ mk) Incomplete table with 1 titration (0mk) Penalise - Wrong arithmetic - Inverted table - Unrealistic titre values (unless explained) Penalise ( ½ mk)for each to a maximum of ( ½ mk)

b) Decimal place (1mk) - Accept only 1 or 2 d.p. consistently, otherwise Penalise fully - Accept inconsistency in the use of zeros as initial burette 0.0 0.00 or 0.000 NB: Decimal point tied to 1st and 3rd row only

c) Accuracy (1mk) Compare the candidate value to the school value (s.v.). If within +0.1 of sv (1mk)within +02 of (s.v.) ( ½ mk) No value within +0.2 (0mk)

d) Averaging (1mk) Values averaged must be shown. - If 3 consistent titrations done and averaged (1mk) - 3 titrations done but only 2 are consistent and averaged (1mk) - If only 2 titrations done are consistent and averaged - 1mk Otherwise penalise fully Calculations a) 12.7 + 12.7 + 12.7 = 12.7( ½ mk)

3

b) i) Moles in 250cm3 = 0.5 = 0.0125 moles ( ½ mk) 40

Moles used = 0.0127 x 25 = 0.00127 (½ mk) 250

(ii) Moles of acid reaction = 0.00127 ( ½ mk)12.7 → 0.00127250 ?

250 x 0.00127 = 0.025 mole ( ½ mk)12.7

iii) Molarity of solution A10cm3 ===> 0.0251000cm3 ===> ?

1000 x 0.025 = 2.5 moles (½ mk10

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(6 mks) Complete table - 6 mks Decimal place tied to 3rd and 5th column (1mk) Accuracy (tied to row (i) to (iv) Trend (Gradual increase in time) (1mk)

b) i) Read from graph (1mk)Value of 1/t (½ mkCorrect answer(½ mk

ii) Increase in concentration increases the rate of reaction. (1mk)2. a)

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Chemistry paper 1, 2&3 KIGUMO SUB-COUNTY CLUSTER EXAMINATION 2016 Kenya National Examination Council

233/1 CHEMISTRY PAPER 1 (THEORY) TIME: 2 HOURS JULY/AUGUST 2016 SECTION A Answer ALL the questions on the spaces provided.

1. a) What is meant by term Isomerism. (1mk)

b) Draw an Isomer of pentene. (1mk)2. Consider the metals copper and zinc.

a) Name one ore for each metal Copper: Zinc:

b) Apart from copper being a good conductor of heat and electricity, state any other physical property of copper.(1mk) 3. a) Define the term fuel. (1mk)

b) State two factors to consider when choosing a fuel. (1mk)4. a) State Graham‟s Law of diffusion. (1mk)

b) A compound contains 29.1% sodium, 40.5% sulphur and the rest is oxygen. Find the empirical formulae.(Na = 23, S = 32, O = 16) (2mks)

5. a) Calculate the maximum volume of oxygen, measured at s.t.p., that can be obtained by heating a solutioncontaining 8.8g of hydrogen peroxide. (2mks)

b) What is a standard solution. (1mk)6. a) State two methods of removing permanent hardness in water only. (1mk)7. Study the flow chart below and answer the question that follows.

Identifyi) Solid V (1mk)ii) Solution R (1mk)iii) Solution Q (1mk)

8. Crystals of hydrated sodium carbonate (Na2CO3.10H2O) left in open air and changed to a white powder.i) Explain what happens and give the relevant equation. (1mk)ii) Give the name of the process shown above. (1mk

9. A student used the set-up shown in the diagram below inorder to study the reactions of some metals with steam. Theexperiment was carried out for ten minutes.

a) What observation would be made if gas H was ignited. (1mk)b) When the experiment was repeated using lead powder instead of Beryllium very little of gas H was obtained. Give a reasonfor this observation. (1mk)

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c) Name another gas which is used together with hydrogen in welding. (1mk)10. Compare the reactivity of chlorine and bromine. (2mks)11. The table below shows the electrical conductivity of substances A, B and C.

a) Give the type of structure and bonding that is present in substance A. (1mk)b) Which substance is likely to be sodium chloride. Explain. (2mks)

12. Hydrogen Iodide is a product formed when hydrogen reacts with Iodine according to the equations.

H2(g) + H2(g) 2HI(g) ÐH = +52.0KJ/mole

Explain how the following would affect the yield of Hydrogen Iodide.a) Increase the temperature. (1mk)b) A decrease in pressure of the system. (1mk)c) State the Le Chatelier‟s principle. (1mk)

13. Explain the following observation made by a form three student.a) Dilute hydrochloric acid does not react with copper metal, but dilute nitric acid does. (1mk)b) Describe briefly how one can distinguish Nitrogen (I) oxide from Nitrogen (II) oxide. (1mk)

14. a) Noble gas are usually unreactive. Explain this phenomena. (1mk)b) Explain the meaning of the term ductility a property found in metals. (1mk)c) Study the diagram below.

Write down the equation for production of gas Q. (1mk)15. The diagram below was used by a student to prepare a certain gas.

a) Write equation taking place in the experiment. (2mks)

b) State why it is advisable to burn the gas. (1mk)

Page | 268

Chemistry paper 1, 2&3 16. Study the flow chart given below.

a) Name substance B. (1mk)b) Give one us of product C. (1mk)c) Write the equation between substance B to form substance C. (1mk)17. The diagram below was used to prepare and collect Sulphur (IV) oxide gas.

a) Identify solid M. (1mk)b) State two properties of SO2 that makes possible to be collected in the method shown. (1mk)c) What are the optimum conditions of conversion of SO2 to SO3. (1mk)

18. During an electrolysis of Zinc sulphate using inert electrodes, a current of 0.5A was passed for 40 minutes on a steadycurrent.a) Write down the equation at the cathode. (1mk)b) Calculate the volume produced at the cathode given that 1F = 96,500c, MGV = 22.4 litres.

(2mks)19. a) Half-life of a radio-active elements is 30 days. Calculate the time required for its activity 37.5 counts per minute.(2mks)

b) Differentiate between an alpha and beta particles. (1mk)20. a) What type of bond is formed when Beryllium and oxygen react. (1mk)

b) Explain why water fetched in rocky areas tend to boil at higher temperature than distilled water.(2mks)

21. a) Copper (II) Sulphate crystals were placed in a beaker containing water. State and explain theobservations made after two days. (2mks)

b) Describe how you can differentiate between Lead (II) ions and Calcium ions using Sodium chloride. (1mk)22. Ethanol obtained from glucose can be converted to ethene as shown below.

a) Name and describe the processes that take place in step I and step II. (2mks)b) State the importance of producing biodegradable plastics and detergents. _______________________________ (1mk)

23. The table below is a part of the periodic table. The letters are not the actual symbols of the element. Study it and answer thequestions that follows.

Page | 269

Chemistry paper 1, 2&3 a) Select an element which is the most reactive. (1mk)b) How do the ionic radius of T and S compared? Explain. (2mks)

24. A mixture of substance K (density 0.626g/cm3) and Z (density 0.85g/cm3) was allowed to settle in a container as shownbelow.

a) Which liquid forms layer (I) (1mk)b) Explain your answer in (a) above. (1mk)c) The chromatogram below shoes the constituents of a flower extract. Study it and answer the question that follows.

Give a reason to explain the different positions of red and yellow pigments. (1mk)25. A student was given a mixture of Lead carbonate and sodium carbonate powders. Explain how you would obtain solid

sodium carbonate, (3mks)26. A compound was analysed and found to contain 24.27% carbonate, 4.08% hydrogen and the rest is chlorine. If the molar

mass of the compound is 99.0, calculate the molecular formula.(C = 12, H = 1, Cl = 25.5) (3mks)

27. a) Write down the equation between burning magnesium and carbon (IV) oxide. (1mk)b) Carbon (IV) oxide does not support combustion yet burning magnesium continues to burn;

Explain. (2mks)28. Draw the following structure.

i) 2-bromo-4-methylpent-2-ene (1mk)ii) Two hydrocarbons compounds are represented by the formulae C4H8 and C4H10.

Which of the compounds is saturated;Explain (2mks)

29. The diagram below illustrates an experiment to investigate the conduction of electricity in liquids. Study it and answer thequestions that follows.

a) State one mistake in the set-up. (1mk)b) If the liquid in the beaker was benzene. State what expected at the bulb? Explain (2mks)

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233/2 CHEMISTRY PAPER 2 (THEORY) TIME: 2 HOURS JULY/AUGUST 2016 SECTION A Answer ALL questions

1. a) State the Hess law. (1mk)b) Use the standard enthalpies of combustion bwlow to answer the questons that follow.

ÐHc0 (graphite = -393KJmol-1

ÐHc0 (C2H6(g)) = -1559.7 KJmol-1

ÐHc0 (H2(g)) = -287KJmol-1 i) Write the equation for the formation of ethane. (1mk)ii) Draw an energy cycle diagram that links the heat of formation of ethane with its heat of combustion and the hets ofcombustion of hydrogen and graphite. (3mks)iii) Calculate the standard heat of formation of ethane. (2mks)f) i) Define molar heat of neutralisaton. (1mk)ii) Explain the difference in molar ethalpies of neutralisation of weak acids and strong acids. (2mks)

2. a)The diagram above shows a set-up used to determine standard electrode potential (E0) of metal x which is higher thanhydrogen in the reactivity series.i) Label part Y. (1mk)ii) Write the equation that takes place at x electrode. (1mk)b) On the diagram, indicate with an arrow the flow of electron through the external conductor. (1mk)c) Study the electrode potentials given below and answer the questions that follow. The letters do not represent actualsymbols of the elements.E0VoltsQ+(aq) +e- → Q(s) -2.290

R2+(aq) + 2e- → R(s) -0.760

S2+(aq) + 2e- → S(s) +0.340T2(g) + 2e- → 2T-(aq) +1.360U+(aq) + e- → U(s) +0.800i) Identify the strongest oxidising agent. (1mk)ii) Calculate the e.m.f. of the cell made by R and U. (2mks)iii) Is it advisable to store a nitrate or solution or metal S in a container made of Q. (2mks)d) Which two of the above elements in an electrochemical cell would produce the longest e.m.f. (1mk)e) Calculate the e.m..f .f the cell chosen in „d‟ above. (2mks)

3. Study the information in the table below and answer the questions that follow.Element Atomic number Melting point (0C)A 11 98.7B 13 660C 14 1410D 17 -101E 19 63.7The letters do not represent the actual symbols of the elements.a) Write the electron arrangement for ions of elements,i) A (1mk)ii) D (1mk)b) Select an element which isi) the most reactive metal. (1mk)ii) the best conductor of electricity. Explain. (2mks)c) State the period and group to which element C belongs.

Group (1/2mk)

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Chemistry paper 1, 2&3 Period (½ mark)d) Compare the reactivity of A and E. (2mks)e) Explain why the atomic radius of B is smaller than that of A. (1mk)f) Describe how a solid mixture of the sulphate of element E and led (II) sulphate can be separated. (3mks)g) Identify any two elements that belong to the same period in the periodic table. (1mk)

4. Below is a chart showing the commercial production of compound D. Study it and answer the questions that follow.

a) Write an equation for the reaction that takes place in the burner. (1mk)b) Name other substances that can be used in place of sulphur in the burner. (2mks)c) Why is it important to purify the products from the burner before being used in the stages that follow? (1mk)d) Give one function of heat exchange. (1mk)e) Give two reasons why Vanadium pentoxide is preferred to Platinised absestos in the process. (2mks)f) i) Name gas A. (1mk)

ii) Why is water not used in place of concentrated sulphuric acid in the absorption tower. (1mk)f) i) Name substances K ,D ( 2 marks)

ii) Give one large scale use of compound D. (1mk)h) Explain the environmental effect of gas A if released to the atmosphere. (2mks)

5. a) i) Crude oil is a source of butane. State the method used to obtain butane from crude oil. (1mk)ii) State one use of butane. (1mk)

b) Study the flow chart below and answer the questions that follow.

i) State the reagent used in step I (1mk)ii) Identify products. Z , N (1mk)iii) State the type of reaction that occurs in step 3. (1mk)iv) Draw the single repeating unit in product Z. (1mk)v) Write a chemical equation in step 3. (1mk)

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Chemistry paper 1, 2&3 c) Using bromine water, explain how you can differentiate between ethyne and product N. (2mks)6. The diagram below shows a blast furnace used to extract iron.

a) State any other iron ore that can used in place of haematite (Fe2O3). (1mkb) i) State impurities found in the iron produced. (1mk)ii) Explain how the impurities above affect the melting point of iron produced. (1mk)c) What is the function of limestone in the blast furnace. Explain. (2mks)d) Identify any substance that is contained in slag. (1mk)e) i) Identify the main reducing agent in blast furnance. (1mk)ii) Write an equation to show how the reducing agent above reacts with the ore. (1mk)iv) State one use of iron. (1mk)f) State the gas recycled in the blast furnance. Explain why? (2mks)

7. a) Other than neutralisation state any other method used to prepare salts. (1mk)b) Describe how to prepare sodium chloride starting with 1M sodium hydroxide. (3mks)c) Write a balanced chemical equation to show effect of heat on calcium carbonate. (1mk)d) Distinguish between a strong base and a weak base. (2mks)e) i) Explain why permanent hardness cannot be removed by boiling. (2mks)ii) State one disadvantage of hard water. (1mk)f) Aluminium oxide reacts with both acids and alkalis. Name any other oxide that behaves like aluminium. (1mk)

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233/3 CHEMISTRY PAPER 2 (practical) TIME: 2 HOURS JULY/AUGUST 2016 CHEMSITRY PAPER 3 CONFIDENTIAL TO SCHOOL

Each candidates to be provided with • Exactly 2.65g of Anhydrous sodium carbonate (Solid P) • 100cm3 of 0.125M Hydrochloric acid labelled solution (M) • FeSO 4.7H2O (Solid C) Approximately 2g • 2g Zinc powder • Maleic acid (solid Q) - 2 sapatulafuls • Universal indicator paper and pH chart • 0.5g of NaHCO 3 labelled • Burrette • Pipette • 250ml Volumetric flask • 2 Conical flask • 2 labels • 100ml measuring cylinder • 250ml beaker • Metallic spatula • 2 boiling tubes • At least 6 test tubes in a rack • Distilled water in a wash bottle

Access to • 2M Pb(NO3)2(aq) supplied with a dropper.• Means of heating• 2M Naoh with a dropper. • 20 vol. H 2O2 with a dropper. • 2M Ba(NO 3)2(aq) with a dropper. • 2M NH 4OH(aq) with a dropper. • Acidified KMnO4 with a dropper. • Acidified K2Cr2O7 with a dropper. • Methyl-Orange indicator.

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233/3 CHEMISTRY PAPER 2 (practical) TIME: 2 HOURS JULY/AUGUST 2016

1. You are provided with- 0.125M HCl labelled solution M. - Anhydrous sodium carbonate labelled solid P. - Methyl orange indicator You are required to prepare a solution of sodium carbonate and standarize it using hydrochloric acid solution M. Procedure Transfer all solid P into a 250cm3 volumetric flask. Add 100cm3 of distilled water and shake until all solid dissolves. Add more distilled water and top up the soluton to 250cm3 mark. Label this as solution T. Using a measuring cylinder measure 50cm3 of solution T and put it in a 250cm3 beaker. Dilute it by adding 50cm3 of distilled water. Shake well to form uniform solution. Label this solution as R. Pipette 25.0cm3 of R into a conical flask. Add two drops of methly orange indicator. Fill the burette with soluion M. Carry out titration. Record your results in the table below. Repeat the titration twice and complee the table. Volume of pipette used ......................................... cm3

a) Calculatei) Average volume of solution M used. (1mk)ii) Moles of solution M used. (1mk)b) Write a balanced equation for the reaction between solution R and M.c) Calculatei) Moles of Na2CO3 in 25cm3 of solution R. (1mk)

ii) Number of moles of Na2CO3 in 100cm3 of solution R. (1mk)

iii) Number of moles of Na2CO3 in 50cm3 of solution T. (1mk)d) Give that Na = 23, C = 12, O = 16

Calculatei) Mass of solid Na2CO3 that was dissolved to make solution T. (2mks)ii) The concentrationof Na2CO3 in soluton T in moles per litre. (1mk)

2. You are provided with solid C. Carry out the tests below. Write your observatins and inferences in the spaces provided.a) Place a spatulaful of C in a boiling tube and heat gently.Observations Inferences(1mk) (1mk)b) Place all the remaining solid C in a boiling tube. Add abount 10cm3 of distilled water and shake well. Divide the resultingmixture into five portions.Observations Inferences(1mk) (1mk)i) To the first portion add ammonia solution dropwise till in excess.Observations Inferences(1mk) (1mk)ii) To the second portion portion add sodium hydroxide dropwise followed by 3 drops of hydrogen peroxide.Observations Inferences(2mks) (1mk)iii) To the third portion add 3 drops of lead (II) nitrate and warm.Observations Inferences(1mk) (1mk)

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Chemistry paper 1, 2&3 iv) To the fourth portion add 3 drops of Barium nitrate. Observations Inferences(1mk) (1mk)

v) To the fifth portion add all the zinc powder provided and warm.Observations Inferences(1mk) (1mk)

3. You are provided with solid Q. Carry out the tests below and record your observations and inferenes in the spaces provided.a) Place a small amount o fQ in a metallic spatula and ignite it over a Bunsen burner flame.Observations Inferences(1mk) (1mk)

b) Place the remaining solid Q in a boiling tube. Add 8cm3 of distilled water and shake well. Dividing the resulting solutioninto four portions.Observations Inferences(1mk) (1mk)

b) To the first portion add acidified potassium manganate (VII).Observations Inferences(1mk) (1mk)

c) To the second portion add acidified potassium dichromate (VI) and warm the mixture.Observations Inferences(1mk) (1mk)d) Test the third portion with a pH paperObservations Inferences(1mk) (1mk)e) To the fourth portion add all the sodium hydrogen carbonate provided.Observations Inferences(1mk) (1mk)

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Chemistry paper 1, 2&3 KIGUMO SUB-COUNTY CLUSTER EXAMINATION 2016 CHEMISTRY PAPER 1 MARKING SCHEME 1. a) Existence of a compound with the same molecular formula but different structural formula

2. a) Copper pyriteZinc blende

b) Malleable, ductileRed metallic lustre (any)Melting point 11000CDensity 8.9g/cm3

3. a) Substance that undergoes combustion readily and gives out heat energyb) Availability

Cost Storage Pollution effects any (2)Heating value

4. a) Under the same conditions of temperature and pressure the rate of diffusion of a gas is inverselyproportional to the square root of its density.

b) Element: Na S O% of mass 29.1 40.5 30.4R.A.M 23 32 16No. of moles 29.1 40.5 30.4

23 32 161.265 1.266 1.9

Na: S : O1.266 1.266 1.9

divide by1.266 1.266 1.9

smallest 1.266 1.266 1.2661 x 2 : 1 x 2 1.5 x 2

x 2 2 2 3

E.F Na2S2O35. a) Equation

2H2O2(l) → 2H2O(l) + O2(g)2 x 34g → 22.4cm3 at s.t.p

Thus 68g of H2O2 yield 22.4 cm3 of O2 at s.t.p8.8g of H2O2 yield ?

= 22.4 x 8.8

68 = 2.89dm3 of O2 at s.t.p

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Chemistry paper 1, 2&3 b) A solution whose concentration is known.

6. - Distillation- Addition of sodium carbonate (Na2CO3)- Use of ion - exchange method (any 2)

7. i) Sulphur (S)ii) Iodine solution (I2(aq))iii) Pottassium chloride (KCl)

8. i) Sodium carbonate looses water of crystallisation to the atmosphere.Na2CO3.10H2O → Na2CO3(s) + 10H2O(l)(ii) efflorescent

9. a) The gas burns with a „pop‟ sound b) Lead is least reactive compared to Berylium thus the reaction is slow hence little amount of hydrogen gas. c) Oxygen

10. Chlorine is more reactive than bromine These is because the electron affinity of chlorine is higher than that of bromine. Reactivity of halogens decrease down the group.

11. a) Metallic bondb) B; Since doesn‟t conduct in solid, but conducts in molten and in aqueous

12. a) More of HI forms i.e. Favours the forward reaction.b) Has no effect, molecules are equal on both sides of the system.c) When a change in conditions is applied to a system in equilibrium , the system moves so as to oppose the change.

13. a) Dilute nitric (V) acid is a very powerfulOxidizing agent hence it can react with least reactive metals. b) Nitrogen (I) oxide relights a glowing splint and has a faint sweet smell, while nitrogen (II) oxide is very unstable.

14. a) Noble gases have their outermost energy level being filled-up hence do not require to loose or gain as the unreactive. b) Property of metal being drawn into wire c) 2HOCl(aq) → 2HCl(aq) + O2(g)

15. a) i) 2H2(g) + O2(g) → 2H2O(l)

ii) 2HCl(aq) + Mg(s) → MgCl2(aq) + H2(g)

b) Mixture of the gas with in explosive hence burned for safety reasons16. a) Ca(OH)2 / Calcium hydroxide

b) Removal of water hardness - Test the presence of CO2 gas (any one )- Raising of pH in acidic soils c) Ca(OH) 2(aq) + 2NH4Cl(aq) →CaCl2(aq) + 2NH4OH(aq)

17. a) Copper / Cu b) Denser than air / Insoluble in liquid x c) Temperature 4500C

Catalyst V 2O5 / Vanadium (V) oxide Pressure 2-3 atmospheres

18. a) 4H+(aq) + 4e-(aq) → 2H2(g)

b) Q = IT= 0.5 x 40 x 60 4F -----> 2 moles 1 mole -----> 22.4 litres= 1200C 4 x 96500 ---> 2 moles 0.00622 ---> ?

1200c ---- 2 x 1200 22.4 x 0.0062296,500 x 4 1

= 0.00622 moles = 0.1393 litresor 139.3cm3

19. a)

No. of half-life 7 @ half-life 30 days Time = 7 x 30

= 210 days

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Chemistry paper 1, 2&3 b) +vely charged , B +vely charged any (1)

high ionizing power in air, than beta are deflected towards -ve plate, Beta towards the plate lower penetrating power than B - particles

20. a) i) Ionic / Electrovalent bondb) Water from rocky have dissolved salts (impurities) than tend to raise the boiling points of these water.

21. a) A blue solution was formed, copper (II) sulphate is soluble in water.b) NaCl with Pb2+ it will form a white ppt due to formation of PbCl2 which is insoluble but with Ca2+ will not.

22. a) Step I : FermentationII: Dehydration

b) Reduces pollution of the environment. 23. a) P

b) S has a bigger ionic radius compared to T; sine T forms ions by loosing electrons and S forms ions by gaining electrons. 24. a) Z

b) Z is denser than K hence settles at the bottom.c) Yellow is highly soluble and less sticky while red is less soluble, but highly sticky.

25. Add water to the mixture and stir. Na2CO3 dissolve while PbCO3 does not. Filter to saturation and allow to cool forcrystallization of Na2CO3 to take place.

26. Element C H Cl% Mass 24.27 4.08 71.65 EF = CH2ClR.A.M. 12 1 35.5No of moles 24.27 4.08 71.65 M = 99

12 1 35.5 12 + 2 + 35.5

2.0225 4.08 2.018 = 99Divide by 2.0255 4.08 2.018 49.5Smallest 2.018 2.018 2.018 = 2

1 2 1M.F. = (CH2Cl)2

= C2H4Cl227. a) 2 Mg(s) + CO2(g) → 2MgO(s) + C(s)

b) Burning Mg produces alot of heat, hence decomposes CO2 into C and oxygen, then O2 is set free and combines withoxygen to form the white solid and black specks of carbon.

28. a)

b) C4H10, it does not contain a double bond or tripple bond.29. a) Electrode L and Electrode K are connected.

b) No lightDoes not contain ions which are responsible for electrical conductivity.

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233/2 CHEMISTRY PAPER 2 (THEORY) TIME: 2 HOURS JULY/AUGUST 2016

1. a) The energy in converting reactants to products isthe same regardless or the root follow. (1mk)b) i) 2C (s) + 3H2(g)

C

- Dry it between filter paper- Evaporate the filtrate to concentrate - Cool the filtrate to form crystals of E sulphate - Dry them between filter paper.

2H6(g) (1mk)

iii) ÐH F(C2H6) = (ÐHC(C) x 2) + (ÐHC(H2) x 3 -ÐHC(C 2H6)= (-393 x 2) + (-286 x 3) - 1.559.7 1mk= 786 + -858 + 1559.7= -84.3Kjmol-1 1/2mkc) i) The heat change that occurs when an acid and a base react to form one mole or water. (1mk)ii) Enthalpy of neutralisation of weak acids is lower than that of strong acids.

Some energy is used to ionise the weak acid. (1mk) 2. (i) y - salt bridge (1mk)

ii) X (s) X2+(aq) +2e-b) From right to left.c) i) T 2ii) Ecell = E reduction - E oxidation

= +0.800 - 076= 1.56V

g) A and B, B and C , C and D4. a) S (s) + O2(g) SO 2(g) ( balance)

b) Ore of copper that contains sulphurie Iron pyrites

Zinc blende ( any one)Copper pyrites

c) To to remove impurities that may poison a catalystd) To regulate hear within the systeme) Cheap

Not easily poisonedf) i) Sulphur (IV) oxide (CO 2)ii) Water produces acid sprays which are harmful to the environmentg) K conc. H 2SO4D: Ammonium sulphate (NH 4)2SO4)ii) Used as a fertilizerg) Causes acid rain- Acid rain corrodes iron sheets- Acid rain lead to death of plants and aquatic animals - Causes breathing difficulties

5. a) i) Fractional distillationii) As a fuel

b) i) Hydrogen chlorideii) Z - Polyvinyl chloride

N - Ethaneiii) Hydrogenation

iv)

Ciii) NOThe container will corrode since S is less reactive than Q.d) Q and T 2e) Ecell = E reduction - E oxidationEcell = +1.36 - 02.92

= 4.28V3. a) i) A+ - 2.8

ii) D- - 2.8.8.b) i) E

ii) BIt has highest number of mobile delocarised electrons c) Group - IV

Period - 3d) E is a more reactive than AE has bigger atomic radius than A.e) B has stronger nuclear fence than A.f) Add water and stir- Filter to obtain lead sulphate as residue

2H2(g) + 2H2(g) →C2H6(g)NB// Not balanced award zero markC - ethyne decolourises bromine water while

ethane does not.- ethyne is unsaturated.

6. a) - Siderite (FeCO 3)- Magnetite (Fe 3O4)b) i) Silicon- Sulphur- Carbon- Siliconii) Impurities lower melting pointc) To form calcium oxide which combines other substances to form slag.d) Calcium silicate (CaSiO 3)- Calcium alluminate (CaAl 2O4)e) i) Carbon (II) oxide (CO)

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Chemistry paper 1, 2&3ii) Fe 2O3(s) + 3CO(g) 2Fe (s) +3CO 2(g)iii) Making iron nails, iron sheets iron boxes, engine blocksf) CO

c) CaCO 3(s) → CaO(s) + CO2(g)d) Strong base Weak base

-pH 12- 14 pH 8 - 11Ionise fully Ionise partially- Good Poor conductor

2- To move the process economical

7. a) Direct synthesis- Precipitationb) Put 20cm3 of 1M sodium hydroxide in a beaker- Add 1M HCl acid (20cm3)- Evaporate the solution to concentration.- Cool the solution to form crystals-Dry the crystals between filter papers.

conduction of electricitye) i) Magnesium and calcium ions present cannot be decomposed by boiling.ii) Boilers scaleStain clothes- Blockage of lead pipes (not water)

f) Lead (II) oxide.

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233/3 CHEMISTRY PAPER 2 (practical) TIME: 2 HOURS JULY/AUGUST 2016

1.

a i) Average volume = 20 + 20 + 20 = 20.0cm33

ii) Moles of solution M used 20 x 0.125

1000 = 0.0025

b) 2HCl(aq) + Na2CO3(aq) → 2NaCl(aq) + CO2(g) + H2O(l)c) i) Moles of Na2CO3 in 25cm3 of solution R.

Mole ratio HCl : Na2CO32 : 1

0.0025 0.00125

ii) Moles of Na2CO3 in 100cm3 of solution R.

0.00125 25cm3? → 100

100 x 0.00125 = 0.005 moles 25

ii) Moles of Na 2CO3 in 50cm3 of solution T = 0.005 moles ( Ans as above)

d) i) Mass of Na2CO30.005 moles → 50cm3

250cm3

= 250 x 0.005 50

= 0.025 moles RFM of Na 2CO3 = 106 Mass = 106 x 0.025

= 2.65g ii) Concentration of Na 2CO3 in moles per litre

0.025 → 250? 1000= 0.1M

2.

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Chemistry paper 1, 2&3 GATANGA FORM FOUR END OF TERM II EXAMINATION 2016Kenya National Examination Council 233/1 CHEMIS TRY (THEORY)PAPER 1

1. A wooden splint was slipped through a region of a particular flame in that laboratory and was burnt as shown in thediagram below.

a) Name the type of flame the splint was slipped through. (1mk)b) Expalin why the splint was burnt the way it is shown in the diagram. (1mk)

2. Elements A and B have atomic masses 23 and 24 respectively. Both of them have 12 neutrons each.a) Write the electron arrangement of A and B.b) Which of the elements has higher ionization energy? Explain. (2mks)

3. A student lowered burning magnesium in a gas jar of carbon (IV) oxide as shown in the diagram below.

a) State and explain the observation made in the gas jar. (2mks)b) Write the equation for the reaction that takes place in the gas jar. (1mk)

4. The figure below shows a set-up used in electrolysis of lead (II) iodide.

a) Why is heating necessary? (1mk)b) Write the equation for the reaction that occurs at the cathode. (1mk)c) At which electrode does reduction occur? (1mk)

5. A mixture contains sodium chloride, ammonium chlorijM and copper (II) oxide. Describe how each substance can beobtained from the mixture. (3mks)

6. Study the diagram shown below and answer the questions that follow. The graph shows the heating curve of water.

a) Is the curve for pure water or impure water? Give a reason for your answer. (2mks)b) Stat the role of each of the following parts during fractional distillation of a mixture of water and ethanol.i) Glass beads in the fractionating column. (1mk)

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Chemistry paper 1, 2&3 ii)Fractionatincolumn.(1mk)

7. The empirical formula of compound A is CH2Br. Given that 0.470g of A occupies a volume of 56cm3 at s.t.p, determineits molecular formula (H = 1.0. C = 12.0. Br = 80.0, Molar gas volume ats.t.p = 22.4dm3) (3mks)

8. Using dots (•) and cross (X) to represent electrons, show the bonding in the folloing compounds.(i) OH- (O = 8, H = 1) (1mk)ii) Li2O (Li = 3, O = 8) (1mk)

9. a) State Charles‟ law. (1mk)b) A balloon contqains 80cm3 of gas at 300C and 4 atmospheres. Calculate the volume of the balloon at 500C and 2atmospheres. (2mks

10. Ethene and ethyne are unsaturated hydrocarbons.a) Explain what is meant by unsaturation in hydrocarbons. (1mk)b) Explain how you would distinguish between ethane and ethene in the lab. (1mk)c) Write an equation for the complete combustion of ethane. (1m

11. Dry sulphur (IV) oxide was passed through two pieces of coloured silk cloth in a gas jar as shown in the diagram below.

a) State the observation made in the gas jar. ( 1 markb) Write equations to explain your observations in gas jar II. (2mks)

12. In an experiment to determine the percentage of magnesium hydroxide in an anti-acid, a solution containing 0.05g of theanti-acide was neutralised by 23cm3 of 0.01M hydrochloric acid.(R.F.M of Magnesium hydroxide = 58)a) Calculate the mass of magnesium hydroxide in the anti-acid. (2mks)b) Determine the percentage of magnesium hydroxide in the anti-acid. (1mk)

13. A student dissolved hydrogen chloride gas in water and methylbenzene as shown in the set-ups below.

a) What is the purpose of the inverted funnel. (1mk)b) A little zinc carbonate was placed in each solution. State and explain the observations that were made. ( 2 marks)

14. The table below shows pH values of some solutions.Solution A B C DpH values 13 7 1 6.5

a) Which solution reacts vigorously with magnesium metal? (1mk)b) Which solution is likely to be lemon juice? (1mk)c) Which solution forms complex ions with zinc (II) oxide? (1mk)

15. a) Define heat of solution. (1mk)b) When 16g of ammonium nitrate was dissolved in 100cm3 of water at 250C, the temperature of the solution drops to190C.Calculate the molar enthalphy of solution of ammonium nitrate (N = 14, O = 16, H = 1, Specific heat capacity of water =4.2kJKg-1k-1 Take density = 1g/cm3) (2mks)

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Chemistry paper 1, 2&3 16. The energy level diagram below shows non-catalysed decomposition of hydrogen peroxide.

a) On the same axis, sketch the graph for the decomposition of hydrogen peroxide when manganese (IV) oxide is added. (1mk)

Label the graph as (a)b) Define activation energy. (1mk)c) The following reaction is in equilibrium in a closed container.C(s) + H2O(g) → CO(g) + H2(g)How would an increase in pressure affect the amount of hydrogen produced. (1mk)

17. The set up below was used by Form 3 students to prepare gas Q. Study it and answer the questions that follow.

a) Identify one mistake made in the set up. (1mk)b) Write an equation for the reaction leading to formation of gas Q. (1mk)c) State one use of gas Q. (1mk)

18. The diagram below shows the radiation emitted by a radioacive sample.

a) Identify radiation W. (1mk)

b) Which of the three radiations would cause most damage to human tissues? Explain your answer. (1mk)c) Explain why it is not safe to store radioactive substances in containers made of aluminium sheets? (1mk)

19. a) What is solubility? (1mk)b) In an experiment to determine the solubility of solid X in water at 300C, the following results were obtained. Mass of evaporating dish = 26.2g Mass of evaporating dish + saturated solution = 42.4g Mass of evaporating dish + dry solid X = 30.4g

Using the information, determine the solubility of solid X at 300C in g/100g of water. (2mks)

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Chemistry paper 1, 2&3 20. The diagram below shows acidic and basic oxides fitted into the general family of oxides.

a) Give the name of the type of oxides that would be placed in the shaded region. (1mk)b) Name one oxide that would be placed in the region. (1mk)c) State one factor taht would accelerate the rate of rusting. (1mk)

21. The set up below was used to prepare dry hydrogen gas. Study it and answer the questons that follow.

a) Identify one mistake in the set up (1mk)b) Name liquid Y. (1mk)c) Explain why helium gas is preferred in weather balloons to hydrogen gas. (1mk)

22. The flow chart below shows some processes involved in the industrial extraction of zinc metal.

a) Name one ore from which zinc is extracted. (1mk)b) Write the equation for the reaction taking place in Unit II. (1mk)

c) Name one use of zinc metal. (1mk)23. i) The diagram below shows part of solvay process.

i) Name solid P (1mk)ii) Write the equation for the reaction that produces solid P. (1mk)iii) What method of separation is used in chamber N? (1mk)

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Chemistry paper 1, 2&3 24. The table below gives some properties of compounds P, Q, R and S.

a) Which of the above compounds is ionic? Explain. (1mk)

b) Select the compound that is a gas at room temperature. Explain your answer. (1mks)

25. Given the following half cells;Pb2+(aq) / Pb(s) EO = -0.13V

Cu2+(aq) / Cu(s) EO = + 0.34V

i) Write the ionic equation for the half cell that undergoes oxidation. (1mk)ii) Calculate the e.m.f. of the cell that would be made.(1mkiii) Determine the oxidation number of chlorine in ClO3. (1mk)

26. A compund has empirical formula C3H6O and a relative formula mass of 116.a) Determine its molecular formula. (2mks)(H = 1.0, C = 12.0, O = 16.0)b) Calculate the percentage composition of carbon by mass in the compound. (1mk)

27. The table below gives some bond energies of some bonds.Bond Bond energy kJmol-1

H - H 435

Cl - Cl 243

H - Cl 431Calculate the enthalpy change for the reaction.H2(g) + Cl2(g) → 2HCl(g) (2mks)

28. Name the class to which the following cleansing agents belong.a) R - COO-Na+ A b)

c) Which cleaning agent is not enviromentally friendly.

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Chemistry paper 1, 2&3 GATANGA FORM FOUR END OF TERM II EXAMINATION 2016Kenya National Examination Council 233/2 CHEMIS TRY (THEORY)PAPER 2

1. The table below shows elements in the periodic table. Use it to answer the questions that follow. The letters are not the actualsymbols of the elements.

a) i) Write the electron arrangement of elements; B and Aii) Write the formula of the compound formed between the elements B and E. (1mk)

b) Element K has atomic number 14. Indicate by use of tick ( ) the position of this element in the table above. (1mk)c) i) he ionization energy of A is higher than that of G. Explain. (1mk)

ii) The atomic radius of C is larger than that of D. (1mk)iii) Compare the reactivity of elements A and B.

Explain your answer. (2mks)d) i) State the name of the group to which elements F and H belong. (1m

ii) Give one use of any of the elements of in group in d(i) above. (1mk)e) The chloride of B is ionic, while the chloride of C is covalent. Explain this observation. (2mks)2. (a) A student wrongly categorised air as a compound and not as a mixture. Give two reasons as to why the student was

wrong. (2mks)(b) The table below shows the results obtained when four solvents were used to separate a dye. Study the results and use them to

answer the questions that follow.Solvent Number of

Solute componentsA 5B 1C 0D 2

i) Identify the most suitable solvent for this separation. Give a reason for your answer. (2mks)ii) What does the result of the solvent C tell us about the dye? (1mk)c) The chromatogram below was obtained from a plant extract. Use it to answer the questions that follow.

i) Name line W (1mk)ii) What does the dotted line represent? (1mk)iii) State with a reason the least soluble dye in the moving solvent. (1mk)d) Below is a list of major component of crude oil and their boiling points.

Component Boiling point (0C)Bitumen Above 400Lubricating oil 350 - 400Petrol 40 - 175Gases Below 40

i) What is the name of the process by which the constituents of crude oil can be separated? (1mk)

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Chemistry paper 1, 2&3 ii) Give one use of the gases component. (1mk)iii) Give the order by which the components are obtained from the mixture, starting with the first. (1mk)

3. An impure solid of magnesium carbonate weighing 9.5g was placed in a beaker containing 50cm3 of dilute nitric (V) acid.The volume of carbon (IV) oxide evolved was recorded at 20 seconds interval in the table below.Time from start of Reaction (sec) 0 20 40 60 80 100 120Volume of CO2 at s.t.p (cm3) 0 650 900 1070 1100 1120 1120

3. a) Write the equation for the reaction between magnesium carbonate and nitric (V) acid. (1mk)b) i) Plot a graph of volume of carbon (IV) oxide (y-axis) against time. (3mks)

ii) From the graph; calculate the rate of reaction betweenI 20 seconds and 40 seconds interval. (2mks)II 40 seconds and 60 seconds interval. (2mks)c) Explain the difference in the reaction rates in I and II. (1mk)d) Why was there no further increase in the volume of carbon (IV) oxide gas after 100 seconds? (1mk)e) How many moles of carbon (IV) oxide were in the maximum volume produced from this reaction? (Molar gas volume at

s.t.p. = 22.4 litres) (1mk)f) What mass of magnesium carbonate will have reacted with the acid after 100 seconds.

(Mg = 24, C= 12, O = 16) (2mks)g) Determine the percentage purity of magnesium carbonate. (2mks)h) Calculate the original concentration of the nitric (V) acid in moles per litre. (2mks)

4. The flow chart below shows some reactions starting with lead (II) nitrate. Study it and answer the questions that follow.

a) i) State the condition necessary in step 1. (1mk)ii) Identify;I Gas Q (1mk)II The acid products S and R (2mks)

b) Write the balanced chemical equations for the reactions in;i) Step3 (1mk)ii)Step 4 (1mk)

c) i) The reaction between lead (II) nitrate and dilute sulphuric (IV) acid starts but stops almost immediately. Explain this observation. (2mks)

ii) Name a suitable reagent that can be reacted with concentrated sulphuric (IV) acid to produceNitric (V) acid. (1mk)

d) In the industrial extraction of lead metal, the ore is first roasted in a furnance. The solid mixture obtained is then fed intoanother furnance together with coke, limestone and scrap iron. State the function of each of the following in this process:a) Coke (1mk)b) Limestone (1mk)c) Scrap Iron (1mk)

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Chemistry paper 1, 2&3 5. a) Candle wax is mainly a hydrocarbon. What is a hydrocarbon? (1mk)

b) Name the following compounds.i)

c) Castor oil extracted from castor seeds is found to change the colour of acidified potassium managanate (VII) .i) State the colour change. (1mk)ii) Explain why castor oil reacts with acidified Potassium mangate (VII) to cause the colour change. (1mkd) Study the reaction scheme below and use it to answer the questions that follow.

ii) Name the process in;Step I (1mk)Step II (1mk)

ii) State the reagent necessary for the process inStep II (1mk)Step III (1mk)

iii) Name the type of reaction taking place in step III (1mk)6. The set up below was used during the electrolysis of acidified water using inert electrodes.

a) Why is the water acidified (1mk)b) What material are the electrodes made of? (1mk)

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Chemistry paper 1, 2&3 c) Identify: Gas A (1mk)

Gas B (1mk) d) On the diagram label;

The Anode:(1mk) The cathode (1mk)

e) During the electrolysis a current of 2 amperes was passed through the acidified water for 21/2 hours. Calculate the volume of gas B produced at rtp. (1 Faraday = 96500C, Molar gas volume at r.t.p = 24000cm3) (3 mks)

7. a) Rhombic sulphur and monoclinic sulphur are allotropes of sulphur. Define Allotropy. (1mk)b)Give two other elements that exhibit allotropy. (1mk)c) Study the flow chart below and answer the questions that follow.

c) Name (i) Compound T (1mk)ii) Gas U (1mk)d) The equation below shows the reaction between sulphur (IV) oxide gas and oxygen gas to produce sulphur (VI) oxide in

contact process.2 SO2(g) + O2(g) → 2SO3 D = -197 kJ/mol

i) State two conditions that are necessary for maximum production of SO3. (2mks)ii) Name the catalyst used for this reaction. (1mk)e) State one use of sulphuric (IV) acid. (1mk)

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Chemistry paper 1, 2&3 GATANGA FORM FOUR END OF TERM II EXAMINATION 2016Kenya National Examination Council 233/1 CHEMISTRY (THEORY)PAPER 1

1. ... .. a) Luminous flame 1mkb) Middle part of the flame not hot due to unburnt gases while the outer part of hot. c) A - 2.8.1

B - 2.8.2 b) Element B It has a smaller atomic radius and therefore higer nuclear attraction.

3. a) The magnesium ribbon confirmed to burn because the reaction is exothermic and produced heatA white powder was formed and black particles MgO and Cb) 2 Mg(s) + CO2(g) → 2MgO(s) + C (s)

White blackpowder particles

4. a) To melt the lead (II) iodide and form free ions (1mk)b) Pb2+(l) + 2e → Pb(s) (1mk)c) Cathode (1mk)

5. First heat the mixture Ammonium chloride sublimes Add water to the remaining mixture) Sodium chloride will dissolve Copper (II) oxide does not dissolve Filter off the copper (II) oxide Heat the filtrate to evaporate sodium chloride

6. a) Impure water (1mk) It does not have sharp melting and boiling points (1mk)b) i) To create a large surface for vapour to form (1mk)ii) To condense the vapour back to liquid before the boiling point. (1mk)

7. E.F. = CH2Br

0.470g ===> 56cm3? ======= (22.4 x 1000)cm3 (22.4 x 1000)cm3 x 0.470 = 188

56 cm3 M.F. = x (E.F) 188 = x (94) (1mk)

x = 2M.F. = 2(CH2Br)= C2H4Br2 (1mk)

8. i)

ii)

ii) Athlete G (1mk) iii) Druge A 1 (1mk)

9. a) Charle‟s law: “The volume of a given mass of gas is directly proportional to its absolute temperature, it pressure beingkept constant.” (1mk)b) P1V1 = P2 V2

T1 T2

V1 = 80cm3T1 = 30 + 273 = 303kP1 = 4 atmT2 = 50 + 273 = 323K

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Chemistry paper 1, 2&3 P2 = 2 atmV2 = P1V1T2

P2T1 (1mk)

= 4atm x 80cm3 x 324k = 170.56cm3 (1mk)2atm x 303k

10. a) Hydrocarbons that do not have maximum number of hydrogen atoms per every carbon atom. They have at least onedouble bond or one tripple bond in the carbon chain. (1mk)b) Flame test - Ethane burns with a clean almost colourless blue flame.Ethene burns with a yellow sooty flame (1mk)

c) 2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(l) (1mk)

11. a) I - The silk cloth was not bleached. It did not turn whiteII - The silk cloth was bleached. It turned white.b) SO2(g) + H2O(l) → H2SO3(aq)H2SO3(aq) 2H+(aq) + SO32- (aq)

SO32- (aq) + Coloured → Colourless productdye + SO42-(aq)

12. Moles of HCl ---- 0.01 moles --- 1000cm3

? --- 23cm3

23 x 0.01 = 0.0023 moles

1000

Mg(OH)2(aq) + 2HCl(aq) → MgCl2(aq) + 2H2O(l)1 : 20.00023 0.00023 moles

2 = 0.00115 moles (1mk) 0.00115 moles x 58 = 0.0667g

b) % = 0.0667g x 100 0.5

= 13.34% 13. a) To provide a large surface area so that the ammonia gas can dissolve uniformly (1mk) or to prevent suck back.

b) I - EfferversceneII - No efferverscence

HCl ionizes in water but it does not ionize in methyl benzene. Water is an ionic solvent while methylbenzene is a non -polar solvent. (1mk)

14. a) C (1mk)b) D (1mk)c) A (1mk)

15. a) Enthalpy change that occurs when one mole of a substance is dissolved in a solvent to give an infinitely dilute solution.b) D H = MCO

M = 100cm3 x 1g/cm3 = 100g = 0.1kg

C = 4.2kJKg-1K-1

O = DT = 60C = 6k

D H = 0.1kg x 4.2kJKg-1x 6k = 2.52kJ

Moles of NH 4NO3= 16 = 0.2 moles(1/2mk) 80

0.2 moles of NH4NO3 loses2.52kJ/mole

1 mole ?0.1 x 2.52 kJ = 25.2kJ/mole

DHO Solution of NH4NO3 = +25.2kJ/mole (1/2mk)

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Chemistry paper 1, 2&3 16. a)

b) Activation energy is the minimu energy required by the reacting particles to cause a successful collision to form products. (1mk) c) An increase in pressure causes a decrease in volume. This favours the backward reaction, shifting the equilibrium to the left. Hence, less amount of hydrogen gas is produced.

17. a) Use of cold water (1mk)b) NH4NO3(s) → N2O(g) + 2H2O(l) (1mk)

c) any one use - Formerly used as an anaesthetic - Used as food additive - Used as oxidiser in racing car engines and rockets - Produce flames for analytical work.

18. a) W - Beta particlesb) R - Alpha particles Alpha particles have the higheest ionising ability / power and thus most damaging. c) Aluminium sheet are not able to absorb all the radiations that are produced by radioactive substances.

19. a) The solubility of a solute in a solvent is the maximum mass of solute required to saturate 100g of the solvent at a particular temperature. b) Mass of solid X ( 30 - 26.2) = 4.2g

Mass of water (42.4 - 30.4) = 12g 4.2 g saturated 12 g of water ? saturates 100g of water ? = 4.2 x 100 = 420

12 12= 35g of solid X. ==> 35g of solid X per 100g of water at 300C.

20. a) Amphoteric oxidesb) Zinc oxide

Aluminium oxide Lead (II) oxide any 1 1 x 1 mk = 1mk

c) Acidic medium Salty medium High temperature any 1 = 1mk

21. a) The downward delivery of hydrogen gas. b) Concentrated sulphuric (VI) acid Rej. dilute sulphuric (VI) acid or

sulphuric (VI) acid c) Helium is relatively inert whilst a mixtre of hydrogen and air is explosive

22. a) Zinc Blende (Zinc sulphide)Calamine (Zinc carbonate) any 1b)ZnO(s) + C(s) → Zn(s) + CO(g) orZnO(s) + CO(g) → Zn(s) + CO2(g)c) Zinc is used as a negative terminal and casing in dry/ Le‟ clauche cells.- Making brass alloy with copper (Cu/Zn)- Galvanisation - a thin layer of molten zinc is formed on the surface of iron.(any 1 = 1mk

23. i) Solid P = Calcium oxideii) CaCO3(s) → CaO(s) + CO2(g)iii) Filtration / Fractional crystallisation

24. a) S - Ionic bond is strong and thus requires a lot of energy to break. Thus, ionic compounds have high melting points andhigh boiling points.b) R - Its boiling point is lower than room temperature.

25. i) Pb(s) → Pb2+(aq) + 2e-, EO = +0.13V

ii) Ecell = EOreduced - EO oxidised= +0.3 - (-0.13)= + 0.34 + 0.13= +0.47Viii) ClO3

y + 3(-2) = 0y - 6 = 0

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y = +6 (1/2mk)

The odixation number of chlorine in ClO 3 is +6

26. a) Molecular formula =(Emperical formula)n n = Molecualr formula mass (MFM)

Emperical formula mass (EFM) EFM = (3 x 12) + (6 x 1) + 16 = 36 + 6 + 16 = 36 + 22 = 58 n = 116 = 2

58 .:Molecualr formula = (C 3H6O)2

= C6H12O2b) C6H12O2Mass of carbon = (6 x 12) 72 % Compositinof carbon = 72 x 100

112 = 64.2857%

28. a) R - COO-Na+ ==> Soapy detergents

b) R O-SO3- Na+ ==> Soapless detergetns

c) R O-SO3- Na+ / Soapless detergent because the do not form scum with hard water

d) R - COO-Na+ / Soapy detergentsSoapless detergents are non-biodegradable / do not decompose and thus pollute the enironment.

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Chemistry paper 1, 2&3 GATANGA FORM FOUR END OF TERM II EXAMINATION 2016Kenya National Examination Council 233/2 CHEMISTRY (THEORY)PAPER 2

1. a) i) B 2.8.2.E 2.8.7

ii) B2+ E-+2 -12 1x1 x2

BE 2 b) Between C and D in the table c) An atom of G has one more energy level than that of A. The valence eletron is therefore more loosely held by the positive nucleus and thus easier to remove. ii) The atom of D has a bigger / stronger nuclear charge than that of C. The number of energy level pulled is the same. iii) A is more reactive than B. This is because A loses only one electron while B looses two electrons to obtain an octet configuration. More ionisation energy is requird for B to react than is required for A. d) i) Noble gases ii) Helium is used in weather balloons. Neon is used in electric lamps. e) The bond between B and chlorine is ionic formed by transfer of electrons from B to chlorine. On the other hand, the bond between C and chlorine is covalent, formed by equal sharing of electrons, hence a molecular compound.

2. A mixture canbe separated by physical means (eg filtration, distillation etc) a compound cannot. - The components of air are not in definite whole number ratio in a compound, the elements are combined in definite whole number ratios, - A compound is a pure substance whilst air is a mixture of several substances. (any (2 x 1) = 2mks b) i) A : It separates the dye to the greatest number of components ie separates the dye the most. ii) The dye is insoluble in the solvent C c) i) Baseline / Origin ii) The solvent front iii) Yellow - It moves the shortest distance from the origin. d) i) Fractional distillation ii) The gases are used as a fuel iii) Gases, Petrol, Lubricating oil, Bitumen

3. a)MgCO3 (s) + 2HNO3(aq) → Mg (NO3)2(aq) + CO2(g) + H2O(l)b) - Scale (at least 1/2 page used)

Label the axis (Both)- Plotting (1mk)Smooth curve (1mk)

ii) 900 - 650 = 250 = 12.5cm3/sec40 - 20 20Working on the graph must be shown

II1070 - 900 = 170 = 8.5 cm3/sec

60 - 40 20Working on the graph must be shown

c) The rate of reaction decreases as time progresses, since the concentration of reactants reduces as the reaction progresses.d) The reactions has reached completion//the reactants are used up.e) 1 mole of CO2 occupies 22400cm3

? ,, ,, ,, 1120 cm3? = 1120cm3 x 1 mole = 0.05 mole of

22400cm3 CO2

f) Mole ratio of MgCO3 : CO21 : 1? : 0.05

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.: Moles of MgCO 3 = 0.5 x 1 = 0.5 mole of MgCO3 1

Mass of MgCO 3 used = R.F.M of x Number of moles MgCO3

= [24 + 12 = (16 x 3)] x 0.05= 84 x 0.05 = 4.2g= 4.2g of MgCO3

g) % purity of MgCO3 = 4.2 x 1009.5

= 44.21% h) Mole ratio of MgCO3 : HNO3 1 : 2

0.05 : ?

.: Moles of HNO 3 used = 0.05 x 2 = 0.1 mole 1

==> 0.1 mole of HNO 3 is in 50cm3 ? 1000cm3? = 0.1 x 1000 = 2.0M

50 4. a) i) Heating

ii) Oxygen gasII S : Nitric (III) acid

R : Nitric (V) acid

b) PbO(s) + H2(g) → Pb(s) + H2O(l)

II) 2HNO2(aq) + O2(g) → 2HNO3(aq)c) i) The reaction produces Lead (II) sulphate which is not soluble in water. Thus, the lead (II) sulphate forms an insoluble layer which prevents further contact between lead (II) nitrate and sulphuric (VI) acid. Hence, the reaction stops. ii) Potassium Nitrate d) a) Coke reduces lead (II) oxide to lead metal b) Limestone produces calcium oxide which combines with silica to form calcium siliate and hence removes silicaimpurities.c) Scrap Iron reduces any remaining lead (II) sulphite to lead metal.

5. Hydrocarbon - a compound that is made up/contains carbon and hydrogen atoms only.b) i) 3 - Methylbut-2-eneii) Proplylethanoate iii) Pentane c)(i) From purple to colourless. ii) Potassium manganate (VII) to cause the colour change. d)Step I -Hydrogenation / Addition of hydrogen Step II - Polymerisation ii) Step II - Nickel catalyst Steip III - Hydrogen chloride , HCl iii) Addition

6. a) To imporve its conducting propertiesb) Graphite or Platinum c) Gas A - Hydrogen gas Gas B - Oxygen gas d) Anode - Electrode on the right

(Labelling should be on the diagram) Cathode: Electrode on the left (Labelling should be on the diagram) e) Gas B = Oxygen

4OH-(aq) → 2H2O(l) + O2(g) + 4e-

.: 4 mole of e- produce 1 mole of O2 (24000cm3)

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.: 4F produce 24000cm3 of O2 Q = It

= 2 x 2.5 x 60 x 60= 18000C

(4 x 96500)C produce 24000cm3 of O218,000C produce ?? = 18000 x 24000 = 119.17cm3

4 x 96500= 1119.7cm3 of O2

7. a) Allotropy is the existence of an element in more than one form in the same physical state.b) Carbon- Phosphorous c) Compound T - Copper (II) Sulphide ii) Gas U - Hydrogen Sulphide d) i) High pressure (2-3 atmospheres) - Low temperature (4500C) ii) Platinum / Vanadium (V) oxide e) - Manufacture of dyes and paints - Manufacture of drugs - Dil. H 2SO4 is used as an electrolyte in lead -acid accumulators. any 1

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Chemistry paper 1, 2&3 KERICHO SUB-COUNTY JOINT EVALUATION Kenya Certificate of Secondary Education (K.C.S.E) 233/1 CHEMISTRY PAPER 1 (THEORY)1. a) The figure below shows some changes in state for a substance X. Study the diagram and answer the questions.

VI II

Solid X Liquid X Gas X III IV

VIEach of the changes can be speeded up by heating or by cooling. Which changes are speeded up by cooling and which onesby heating. (2 marks)

b) Magnesium sulphate may be used as a laxative. What does this term laxative mean ? (1 mark)2. Both molten sodium chloride and molten sodium metal conducts electricity. Explain how each of these conducts electricity.

(i) Molten sodium chloride (1 mark)(ii) Molten sodium metal (1 mark)

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

Step 3 WaterSO 3(g)O 2

SO 2(g) AStep 2 Step 1H2S(g) KOH (aq)

C+D B a) Name the substance A and B (1 mark)

b) State the property of SO2 exhibited in step 2. (1 mark)4. Study the energy level diagram below and answer the questions that follow.

Energy(KJ) 80

706050

Reactants403020 Products10

0 Reaction Path

(i) State and explain whether the reaction represented is endothermic or exothermic. (1 mark)ii) From the diagram, determineI. the activation energy (1 mark)II. enthalpy of reaction (1 mark)

5. The following chromatogram was obtained in an experiment to investigate the components present in certain dyes.

A B C D

a) Which two dyes when mixed would produce A ? (1 mark)b) Which dye is pure ? (1 mark)c) Indicate on the diagram the solvent front. (1 mark)

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Chemistry paper 1, 2&3 6. Two elements X and Y are represented as shown below.

i) Write the formula of the compound formed when X and Y react. (1 mark)ii) State the family name to which element X belongs. (1 mark)iii) Element Y has a mass number of 40, how many neutrons are present in its nucleus ? (1 mark)

7. a) State Graham‟s law of diffusion. (1 mark)b) If it takes 30 seconds for 100cm3 of carbon IV oxide to diffuse across a porous plate, how long will it take 150cm3 ofnitrogen IV oxide to diffuse across the same plate under similar conditions ?(C = 20, N = 14, O = 16) (2 marks)

8. a) Give the IUPAC names of the following compounds (2 marks)i) CH3(CH2)CH2OH ii) CH3CH2CH(CH3)COOH b) Given the following polymer, draw the structure of the monomer. (1 mark)

9. In an experiment, rods of metal X, Y, Z were cleaned with sand paper and placed in a beaker containing water. Another set of rods was also placed in a beaker containing dilute acid. After placing the rods in the two liquids, bubbles of gas were seen around some of the rods as shown in the diagram below.

X Y Z X Y Z

Dilute Acid

Water

BubblesBubbles

a) Why is it necessary to clean the rods with sand paper before dipping them into the liquid. (1 mark)b) Arrange the three metals in order of their reactivity starting with the most reactive. (2 marks)

10. The grid below is part of periodic table. Use it to answer the questions that follow. (The letters do not represent the actualsymbols of the elements)

R SN Q T UP

a) Indicate in the grid the position of an element represented by letter V, whose atomic number is 14. (1 mark)b) Select a letter which represents a mono atomic gas. (1 mark)c) Write an equation for the reaction between Q and T. (1 mark)11. The set-up below shows how gas A, was prepared and reacted with heated magnesium.

Magnesium Excess gas A

Heat

Ammonium nitrite

Heat a) Give a reason why it is not advisable to heat magnesium before heating ammonium nitrite. (1 mark)b) i) Identify gas A. (1 mark)ii) Write a chemical equation for the reaction between gas A and magnesium. (1 mark)

12. a) Radioactive polonium - 216 decays as shown below.216 208

84 Po Pb + m + n82

Determine the value of m and n. (1½ marks)c) The table below gives the rate of decay of a radioactive element Y.

Calculate the half life of the radioactive element Y. (1½ marks)

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Chemistry paper 1, 2&3 13. Study the table below and use it to answer the questions that follow.

Solution PH

A 3.5

B 14

C 8.5

(i) In which of the solution will phenolphthalein indicator be colourless. (1 mark)(ii) Which of the solutions could be used to relieve heartburn ? Explain. (2 marks)

14. Given the following reagents; solid sodium carbonate, solid lead (II) nitrate, water. Describe how a sample of lead (II)carbonate can be prepared in the laboratory. (3 marks)

15. The table below shows the tests carried out on separate sample of water drawn from a well and the results.

Test Results

i) Addition of excess aqueous ammonia White precipitateii) Addition of a few drops of dilute sulphuric

VI acid No precipitate formediii) Addition of dilute hydrochloric acid

followed by few drops of barium chloride White precipitate

a) Identify the possible cations and anions present in the water. (2 marks)b) Write an ionic equation for the reaction which takes place in test tube (iii). (1 mark)16. (a) A mass of 40g of a saturated solution of potassium chlorate at 25oC yields 14 of potassium chlorate when evaporated to

dryness. Calculate the solubility of potassium chlorate at 25oC. (2 marks)b) State one advantage of hard water. (1 mark)

17. a) Why is air considered as a mixture rather than a compound ? (1 mark)b) State one similarity between rusting and combustion of iron. (1 mark)c) Explain why iron nails rust faster in sodium chloride solution than in tap water. (1 mark)

18. The flow chart shows the extraction of zinc metal from its chief ore. Study the flow chart and answer the questions that follow.Gas K

CokeStep 1

Chief Ore Roasting Furnace Smelting Furnace

Le ad spray Zinc L

a) Name the chief ore used in the process. (½ mark)b) Write equation for the reaction in the roasting furnace ? (1 mark)c) State the functions of the lead spray. (1 mark)d) Give one use of zinc. (½ mark)

19. The apparatus shown below was used to investigate the effect of carbon II oxide on copper II oxide.

Copper IIOxide Blue flame

Drycarbon II Oxide

Heat Tube K

a) State the observation that was made in the combustion tube by the end of the experiment. (1 mark)b) Write an equation for the reaction that took place in the combustion tube. (1 mark)c) Why is it necessary to burn gas coming out of tube K ? (1 mark)

20. When 10g of a mixture of potassium chloride and anhydrous sodium sulphate is dissolved in water and excess bariumchloride solution added, 6.9g of Barium sulphate is precipitated. Calculate the composition of the mixture. (K = 39, Cl =35.5, Na = 23, O = 16, Ba = 137) (3 marks)

21. When bismuth III chloride is added to water, a reaction occurs and a white precipitate forms as shown below.BiCl3(aq) + H2O(l) BiOCl(s) + 2HCl(aq)

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Chemistry paper 1, 2&3 What would be the effect on the amount of the precipitate formed if sodium hydroxide solution is added to the equilibrium mixture ? Explain your answer. (2 marks)

22. The set up below was used to investigate some properties of chlorine gas.

Substance G

MnO2

Drying a) Name : agent

i) Substance G (1 mark)ii) A suitable drying agent. (1 mark)b) What property of chlorine make it possible for it to be collected as shown in the diagram ? (1 mark)

23. What volume of oxygen gas at r.t.p will be liberated at the anode when a current of 3 amperes is passed through magnesiumsulphate solution for 45 minutes and 30 seconds. (Molar gas volume at r.t.p = 24000cm3, Faraday constant = 96500Coulombs) (3 marks)

24.a) What is air pollution ? (1 mark)b) State four gaseous substances present in unpolluted air. (2 marks)

25. The labels of two reagent bottles contained the following safely symbols.

Bottle A Bottle B

a) What do the symbols mean ? Explain. (2 marks)b) Which of the reagent is more harmful ? (1 mark)26. The table below shows properties of some chlorides. Study it and answer the questions that follow.

Chloride Mp(°C) BP (°C) Electrical conductivity in aqueous solution PH of solution

Al - 183 Good 3Na 860 1420 Good 7

P 32 75 Good 3

H -146 -29 Good 1

a) Explain the high melting and boiling points of sodium chloride. (1 mark)b) Write an equation for the reaction between PCl5 and water. (1 mark)c) Draw the dot (•) and cross (x) diagram to show bonding in NaCl. (1 mark)

27. The cell convention for and electrochemical cell is shown below.Zn(s) / Zn2+(aq) // Pb2+(aq) / Pb(s)

a) Name two substances that can be used as electrolytes in the above cell. (1 mark)b) Which of the electrodes is the negative in the cell above ? Explain. (2 marks)

28. Excess concentrated sulphuric VI acid was mixed with pieces of dry wood as shown.

Concetrated Sulphuric VI acid

Dry wood

a) State the observation made in the tube. (1 mark)b) When the reaction was complete, the mixture was heated gently, then strongly and set up adjusted as shown below.

Acidified potassiumchromate VI Solution

Heat

State and explain the observation made on acidified potassium chromate VI solution. (2 marks)

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Chemistry paper 1, 2&3 KERICHO SUB-COUNTY JOINT EVALUATION

Kenya Certificate of Secondary Education (K.C.S.E) 233/2 CHEMISTRY PAPER 2 (THEORY) 1. Study the table below and answer the questions that follow. The letters do not represent the actual symbols of the elements.

Formula of ion Electron configuration

A2+ 2.8

B3+ 2.8

C- 2.8.8

D- 2.8

E2+ 2a) Select elements found in :

i) The same group (1 mark)ii) Period three (1 mark)iii) What is the family name given to the group to which elements identified in a(i) above belongs. (1 mark)

b) How does the atomic radius of element B and A compare. Explain. (2 marks)c) State two industrial use of element B. (2 marks)d) With reason, compare the reactivity of C and D. (2 marks)e) Write the formula of compound formed when A and D react. (1 mark)f) What type of bond is formed when element E react with oxygen. Give a reason for your answer. (2 marks)2. The diagram below represents a set up that was used for electrolysis of aqueous copper (II) nitrate.

Battery

SyringeGas X

Carbon Carbon electrode A

electrode B Copper

(II ) nitra te

a) A gas that relights a glowing splint was produced at electrode A. i) Which electrode is the cathode ? Explain. (2 marks)ii) State another suitable method for collecting gas X. (1 mark)iii) Write ionic equations to show reactions that take place at the :

Anode (1 mark)Cathode (1 mark)

iv) Explain how the identity of the product at the cathode of this electrolysis can be confirmed. (2 marks)v) Calculate the mass of copper deposited if a constant current of 5A was passed for 3 hours.

(Cu = 63.5, 1F = 96500C) (2 marks)

b) The following are standard electrode potentials for some electrodes. The letters do not represent tthactual symbols of the elements.

Element Eq (volts)A2+(aq) + 2e- A(s) -2.93B2+(aq) + 2e- B(s) -2.38C2+(aq) + 2e- C(s) 0.00D2+(aq) + 2e- D(s) +0.34VE+(aq) + e- E(s) +2.87V

i) Which is the strongest reducing agent ? Explain. (2 marks)ii) Write the cell representation for the electrochemical cell obtained by combining the half cell of B and D. (1 mark)iii) Calculate the e.m.f of the cell in (ii) above. (2 marks)

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Chemistry paper 1, 2&3 3. Study the flow chart below and answer the questions that follow.

C3H8

Step I

Propanoic acid

Conc .H+

CH3CH = CH2

Step IIStep V

CH3CH2CH2O H

2 SO4 Step IV

Step III

Potassium step VII

CH3

CH CH 2 n

Liquid X + Gas M

Step VI Ethanol and heat

Substance L

Sugars

a) i) Name the type of reaction in the following steps :

I. Step III (½ mark)II. Step IV (½ mark)

ii) Name the important reagents and conditions in : Step I : Reagent (1 mark)Condition Step II : Reagent (1 mark)ConditionStep V : Reagent (1 mark)Condition

b) i) Write a balanced equation for the reaction taking place in :Step VI (1 mark)Step VII (1 mark)ii) Give the systematic name of liquid X and substance LLiquid X (½ mark)Substance L (½ mark)

d) i) If the relative molecular mass of compound formed in step III is 42,000, determine the value ofn in the compound. (C = 12.0, H = 1.0) (2 marks)

ii) State one disadvantages of continued use of items made from the compound formed in d(i) above. (1 mark)4. a)Define the following terms :

i) Atomicity (1 mark)ii) Molar gas volume (1 mark)b) i) State Gay-Lussac‟s law. (1 mark)

ii) A sample of 10cm3 of hydrogen sulphide was burned in 40cm3 of oxygen. Calculate the volume and composition ofresidual gas (assume all volumes are measured at s.t.p) (2 marks)

c) i) Calculate the mass of sodium carbonate contained in 200cm3 of 0.02M sodium carbonate solution. (2 marks)ii) 0.239g of copper (II) oxide was placed in a conical flask. Calculate the volume of 0.1M solution of hydrochloric acid

that would completely react with copper (II) oxide in the conical flask. (O = 16.0, Cu = 63.5, H = 1.0, Cl = 35.5)(2 marks)

d) Find the mass of 5.2 x 1023 atoms of sodium. (Na = 23.0, L = 6.023 x 1023) (2 marks)

5. a) Starting with lead (II) carbonate, describe how a solid sample of lead sulphate can be prepared. (3 marks)b) Water was added to lead (II) nitrate by a student. She divided the resulting solution into four, state the observation madeafter subjecting them to the following tests:i) To the first portion she added sodium hydroxide dropwise until in excess. (1 mark)ii) To the second portion she added ammonia solution dropwise until in excess. (1 mark)iii) To the third portion she added hydrochloric acid and warm. (1 mark)iv) To the last portion she added sodium iodide solution. (1 mark)v) Write an ionic equation for the reaction in test (iv) above. (1 mark)c) State two commercial uses of sodium carbonate obtained in Solvay process. (2 marks)

6. The following diagram was used to study a property of hydrogen gas. Study it and answer the questions that follow.Copper II )Oxide(

Point ZDry

hydrogenAnhydrous Copper

(II )Sulphate

a) Name the missing condition in the above set up. (1 mark)b) Explain why the combustion tube is clamped in a slanting position. (1 mark)

c) Before lighting the gas at the end of delivery tube, hydrogen must be let to pass through until all the air is driven out. Explain.(1 mark)

d) State three observations that occur in the combustion tube. (3 marks)e) Why was hydrogen gas burnt at point Z. (1 mark)

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Chemistry paper 1, 2&3 f) Why should the supply of hydrogen gas be continued while the apparatus cool. (1 mark)g) What would be observed if the experiment was repeated using lead (II) oxide. (1 mark)h) Other than the property investigated above, name two other chemical properties of hydrogen gas. (2 marks)i) State two industrial use of hydrogen gas. (2 marks)7. The extraction of aluminium from its ore takes place in two stages; purification stage and electrolysis stage. The diagram

below shows the set up for electrolysis stage.

Aluminium

a) i) Name the ore from which aluminium is extracted. (1 mark)ii) Name one impurity which is removed at the purification stage. (1 mark)

b)i) Label on the diagram each of the followingI. AnodeII. CathodeIII. Region containing the electrolyte (3 marks)

ii) The melting point of aluminium is 2054oC but electrolysis is carried out between 800-900oC.I. Why is electrolysis not carried out at 20540C (1 mark)

II. What is done to lower the temperature ? (1 mark)iii) The aluminium which is produced is tapped off as a liquid. What does this suggest about its melting point ? (1 mark)

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Chemistry paper 1, 2&3 KERICHO SUB-COUNTY JOINT EVALUATION Kenya Certificate of Secondary Education (K.C.S.E) 233/3 CHEMISTRY PAPER 3 (PRACTICALS) 1. You are provided with : - Solution A, 0.15M solution thiosulphate - Solution B, 2M hydrochloric acid - Solution C, a solution of basic solution (0.2M X (OH)n)

You are required to determine the rate of reaction between hydrochloric acid solution B at different concentrations of sodium thiosulphate solution A.

Procedure 1

Draw a cross (x) on a piece of white paper using a pencil. Measure 30cm 3 of a solution A using a measuring cylinder and put it into a 100ml glass beaker placed over a white piece of paper drawn above. Measure 10cm3 of hydrochloric acid solution B using a 10ml measuring cylinder and add to the beaker, start the stopwatch. Immediately swirl the mixture. View the cross from above the mixture in the beaker. Stop the clock when the cross just disappears. Record the time taken in the table below. Repeat the above procedure using volumes of solution A, water and solution B as indicated in the table below. TABLE 1

Concentration of Time for X toVolume of Volume of Volume of solution A disappear Rate =

Experiment solution A (cm³) water (cm³) solution B (cm³) (moldm-3) (seconds)

1 30 0 10

2 25 5 10

3 20 10 10

4 15 15 10

5 10 20 10

6 5 25 10(5 marks)

a) Plot a graph of rate (S-1) against volume of solution A (cm3) (3 marks)b) From the graph determine :i) The rate of reaction when 19cm3 of solution A was used. (1 mark)

ii) The time taken for X to disappear when 12cm3 of solution A was used. (1 mark)iii) Determine the time taken for X to disappear if 3cm3 of water was used. (1 mark)c) How does the rate of reaction relate to the concentrations of reagents ? (1 mark)Procedure II Using a clean 100ml measuring cylinder measure exactly 25cm3 of solution B into a 250cm3 volumetric flask. Add distilled water upto the mark. Labe this as solution D. Fill a burette with solution D. Using a pipette and a pipette filler place 25cm3 of solution C into a 250ml conical flask. Add two drops of methyl orange indicator and shake. Titrate it with solution D and record your results in table II. Repeat the titration two more times and complete the table.

Table II

I II III

Final burette reading (cm³)

Initial burette reading (cm³)

Volume of solution D added (cm³) (4 marks)

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Chemistry paper 1, 2&3 a) Determine the :

ii) moles of hydrochloric acid in solution D used. (2 marks)iii) moles of the alkaline solution C used. (1 mark)

b) Find the mole ratio for the reaction between solution A and solution C. (1 mark)c) Hence determine the oxidation state of metal X. (1 mark)2. You are provided with substance M for this question. Transfer the substance into a clean boiling tube. Add about 10cm3 of

distilled water and stir. Pour the mixture into four clean test tubes of about 2cm3 each.

Observations Inferences1 mk 1 mk

a) To the first portion of the solutions, add sodium hydroxide solution dropwise until in excess.


b) Dip a clean stirring rod / glass rod / nichrome wire into the second portion and then place into the side of a bluebunsen flame.


c) To the third portion, add 2-3 drops of barium nitrate solution followed by excess hydrochloricacid.


d) To the fourth portion, add 2-3 drops of acidified potassium manganate (VII)


3. You are provided with substance W for tests in this question.

a) Place 3 drops of substance W on a clean dry watch glass and ignite it.


b) Place about 2cm3 of substance W in a clean dry test tube, then add all the sodium hydrogencarbonate provided.


c) Place about 2cm3 of substance W in a test tube then add about 1cm3 of acidified potassiummanganate (VII) and warm the mixture.


d) Place about 2cm3 of substance W in a test tube then add 2-3 drops of bromine water.


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Chemistry paper 1, 2&3 KERICHO SUB-COUNTY JOINT EVALUATION 233/1 CHEMISTRY PAPER 1 (THEORY) MARKING SCHEME 1. a)Cooling - III, IV, VI

Heating - I, II, V c) A laxative is a drug used to cause one to empty his bowels

2. i) Mobile ionii) Delocalised electrons

3. a) i) A - H2SO3 - sulphuric IV acidB - K2SO3 - potassium sulphiteb) Oxidising property

4. i) Exothermic; products at lower energy level than the reactantsii) Activation energy = 60 - 40

= 20KjmolEnthalpy of reaction = 20 - 40

= -20Kjmol5. a) C and D

b) Bc) On the diagram above top spots

6. i) YX2

ii) Halogensiii) 40 - 20 = 20

7. a) Under the same conditions of temperature and pressure, the rate of diffusion of a gas is inversely proportional to the squareroot of its density

b) RCO2 MNO 2

RNO 2 MCO 2

3 33 46

RNO 2 44RNO2 = 3.33

1.0225= 46.058 se

8. a)i) Propan-1-olii) 2-methybutanoic acid

b)

9. a) To remove oxide coating which couldinhibit reactionb) YZX - reactivity decreases

10. a) On the grid - group (IV) period 3b) Uc) Q(s) + T2(s) QT2(s)

11. a) Magnesium would react with air in the combustion tube since nitrogen gas has not yet been producedb) i) Nitrogen gasii) 3Mg(s) + N2(g) Mg3N2(s)

12. a) 216 - 208 = 88 = 4m + 0 m = 8/4 = 2, a ( He) 84 = 82 + 4 + n 84 = 86 + n n = 84 - 86 n = -2 n = 2 b

b) ( ) 5t½ = 270 t½ = 270 = 54 days

5 13. i) A

ii) C - it is weakly alkaline hence neutralise excess acid in the stomach safely14. - add enough water to Pb(NO3)2 to form a solution

- add enough water to Na2CO3 to form a solution- mix the two solution to form PbCO3 precipitate

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Chemistry paper 1, 2&3 - filter the mixture to obtain PbCO3 as residue - rinse the PbCO3 with distilled water and - dry between filter paper

15. a) Al3+, SO2-4

b) Ba2+(aq) + SO2-4(aq) BaSO4(s)

16. a) Mass of KClO3 = 14g Mass of water = 26g 14g of KClO3 26g of water

100g of water 14 x 100 = 53.846g/100g of water

26 b) Ca2+ are useful for development of strong bones and teeth

17. a) Can be separated using physical means b) Both processes uses oxygen in the reaction

c) Sodium chloride is a substance that accelerate rusting while tap water contains moisture and oxygen conditions necessary for rusting to occur

18. a) Zinc blende b) 2ZnS(s) + 3O2(g) 2ZnO(s) + 2SO2(g)

c) - prevents reoxidation of zinc - condense zinc vapour d)- making dry cell causing - making brass

- galvanising iron sheets - manufacture of paints

19. a) Black solid change to brown b) CuO(s) + CO(g) Cu(s) + CO2(g)

c) CO is poisonous when inhaled20. Na2SO4(s) + BaCl2(aq) BaSO4(s) + 2NaCl(aq)

Moles of BaSO4 = 6.9 = 0.02961 moles 233

Mass of Na2SO4 = 0.02961 x 142 = 4.2046 Mass of KCl = 10 - 4.2046

= 5.7954g 21. Increased - HCl is used thus the rate of forward reaction is favoured or NaOH neutralise HCl, hence reaction proceeds faster

in forward reaction to produce more HCl 22. a) i) Concentrated HCl

ii) Concentrated sulphuric (VI) acid b) It is denser than air

23. 4OH-(aq) 4e- + 2H2O(l) + O2(g)

4F produces 1 mole of O2 of 24000cm3

4x 96500C = 38600C produces 24000cm3

Q= It 3 x 145 x 60 + 30 = 8190C = 386000C produces 24000cm3 O2

8190C produce 81900 x 24000 386000

= 509.2227cm3 of O2

24. a) Addition of undesirable substances to the air b) Oxygen, nitrogen, carbon (IV) oxide inert gases

25. a) A - toxic - is poisonous and cause death if swallowed

B - irritant- may cause blisters and if inhaled cause coughing

b) Reagent in bottle A26. a) Giant ionic structure with strong ionic bonds between particles

b) PCl5(s) + 3H2O(l) H3PO4(aq) + 5HCl(aq)+ -

c) OR+

Na + Cl Na Cl

27.a) Soluble salts of the two saltsb) Zinc loses electrons (oxidation) as Zn2+ ions goes into solution leaving electrons on the zinc rod making it negatively

charged28. a) - Dry wood changes to black

- bubbles of colourless gasb) Acidified K2Cr2O7 changes from orange to green Conc. H2SO4 reduced to SO2 which reduce acidified Cr2O2-7 to

chromium ions (Cr3+) which are green in colour

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Chemistry paper 1, 2&3 KERICHO SUB-COUNTY JOINT EVALUATION Kenya Certificate of Secondary Education (K.C.S.E) 233/2 CHEMISTRY PAPER 2 (THEORY) MARKING SCHEME1. a)i) A and E or C and D

ii) A, B and Ciii) Alkaline earth metals if A and E or halogens if C and D

b) Atomic radius of B is smaller than that of A. B has stronger nuclear charge due to more protonshence pull the energy levels closer to the nucleus compared to A which has less protons

c)- Making aircrafts parts since its light- Making electrical cables since it is a better conductor of electricity- Extraction of metals like iron

d) D is more reactive than C, D has smaller atomic radius hence can attract the incoming electron more easily compared to C which has a larger atomicradius

e) AD2

f) Ionic bondThere is complete transfer of electrons from E to oxygen

2. a) i) B - oxygen gas is liberated as a result of thedischarge of OH- ion which are attracted byanode A hence B becomes

the cathodeii) Over wateriii) Anode4OH-(aq) 2H2O(l) + O2(g) + 4e-

CathodeCu2+(aq) + 2e- Cu(s)

iv) Dissolving in nitric (V) acid and adding excessaqueous ammonia to the solution. A deep bluesolution of [Cu(NH3)4]2+ is

formedv) Q = It

= 5 x 3 x 60 x 60= 54000C

Cu2+(aq) + 2e- Cu(s)

2 x 96500 = 193000C193000C 63.554000C ?54000C x 63.5

193000= 17.77g

b) (i) A - has the highest ability to lose electrons(ii) B(s) /B2+(aq) // D2+(aq) / D(s)

iii) E = Ered - Eoxid.

+0.34 - (-2.38)= +2.72V

OrB(s) B2+(aq) + 2e- + 2.38

D2+(aq) + 2e- D(s) +0.34

E = +2.38 + (+0.34)

= 2.72V3. a) i) I Polymerisation ½

II Fermentation ½ii) Step I

Reagent - hydrogen gas ½Condition - nickel or platinum ½

Step IIReagent - concentrated sulphuric (VI) acid ½ Condition - temp (160o - 180o) ½

Step VReagent-acidified potassium manganate (VII) Condition - heatb) i) Step VICH3CH2COOH + CH3CH2OHCH3CH2COOCH2CH3 + H2O

Step VII2CH3CH2CH2OH + 2K 2CH3CH2CH2OK + H2(g)

ii) Potassium propoxide ½Ethylpropanoate ½

c) - C3H6 decolourises acidified KMnO4 while C3H8 donot- C3H6 decolourises brown / yellow HOBr while C3H8 do not- C3H6 burns with sooty flame C3H8 burns with blue flameany two (2mks)

d) i) [C3H6]n = 42000 142n = 4200042 42n = 1000 1

ii) Non-biodegradable4. a) i) Number of atoms of an element in one molecule

ii) Volume occupied by one mole of a gas at s.t.p orr.t.p

b) i) When gases react, they do so in volumes which bear simple ratio to one another and to the volume of gaseous products provided all volumes are

measured at standard temperature and pressure ii) 2H2S(g) + 3O2(g) 2SO2(g) + 2H2O(l)

2 vol 3 vol 2 vol10cm3 40cm3 10cm3

2 vol 10cm3

3 vol 3/2 x 10 = 15cm3

Amount remaining 40 - 15= 25cm3

total volumes = 25 + 10= 35cm2

made up of 10cm3 of SO2 and 25cm3 of oxygen c) i) 1000cm3 of Na2CO3 0.02 moles

200cm3 200 x 0.02

1000 = 4.0 x 10-3moles

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1 mole of Na2CO3 106 ii) White precipitate insoluble in excess ½40 x 10-3 ? iii) White precipitate soluble on warming ½

4.0 x 10-3 x 106 iv) Yellow precipitate1 v) Pb2+(aq) + 2I-(aq) PbI2(s)

= 0.424g c) - Making glassii) CuO(s) + 2HCl(aq) CuCl2 + H2O(l) - Softening hard water

1 : 2 - Making sodium silicate used in detergentsMoles of CuO = 0.239 making

79.5 6. a) Heat= 3.006 x 10-3 mol b) For condensed vapour not to flow back to the

Mole ratio 1 : 2 tube which might break itMoles of HCl = 3.006 x 10-3 x 2 c) Prevent mixing of air and hydrogen that causes

= 6.0125 x 10-3 explosion0.1 moles of HCl 1000cm3 d) - black copper (II) oxide change to brown6.0125 x 10-3 ? - colourless liquid collects at the cooler parts6.0125 x 10-3 x 1000cm3 - white anhydrous CuSO4 change to blue

0.1 e) When hydrogen come in contact with air, it= 60.125cm3 explode if ignited hence it is burned to avoid being

d) 23g Na contains 6.023 x 1023 atoms release to air5.20 x 1023 atoms f) Prevent reoxidation of copper metal by air

23g x 5.20 x 1023 atoms g) Yellow lead (II) oxide will change to orange then6.023 x 1023 grey= 19.8572g h)- burns with a blue flame

5. a) - to HNO3 add excess PbCO3 as you stir until - neutral to litmus paper

effervescence stop 7. a) i) Bauxite- filter the mixture and collect Pb(NO3)2 as filtrate ii) Silica or iron (III) oxide- add soluble sulphate solution e.g. Na2SO4 to b) i) On the diagramPb(NO3)2 to get PbSO4(s) and NaNO3(aq) ii) I. It is expensive to maintain hence- filter the mixture and collect PbSO4 as residue uneconomical- rinse the residue and dry between filter paper II. Cryolite is added

b) i) White precipitate soluble in excess ½ iii) Lower than operating temperature

KERICHO SUB-COUNTY JOINT EVALUATION Kenya Certificate of Secondary Education (K.C.S.E) 233/3 CHEMISTRY PAPER 3 (PRACTICAL) MARKING SCHEME Table 1

Expt Vol. of A Vol of water Vol of B Conc. of A Time 1/time

1 0.15

2 0.125

3 0.1

4 0.075

5 0.05

6 0.025Complete table 2mks Penalise

- ½ for unrealistic time (time 1 - should not be less than 10 sec. or more than 100 sec) - ½ for each empty space (to a maximum of 2mks Trends 1mk- penalise 1mk for time that is constant or decreasingDecimal place 1mk- accept 4d.p or 1/t

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Chemistry paper 1, 2&3 Accuracy 1mk - all arithmetic are correct+2 seconds to S.V - burette readings are realistic

otherwise penalise to a max 1mka) Graph

Scale ½mk Decimal place 1mk- constant scale throughout both axes - Either if all readings are upto 1d.p- plots cover at least ½ of graph on both axes or if two readings are upto 2d.p with the second digit asLabelling ½mk 0 or 5- both axes labelled and correct units shownPlots 1mk Accuracy 1mk- 1mk if at least five plots are correct - accept at least one titre within +0.1 of S.V for 1mk- ½mk if at least four plots are correct 0mk + 0.2 of S.V for ½mk

otherwise Principle of averagingCurve 1mk - accept 2 or 3 consistent titres correctly chosen for- 1mk if best line of fit drawn which must pass through ½mkthe origin - accept correct average for correct titres for ½mk

b) i) - ½mk for showing on reading on graphs- ½mk for correct reading of point shown (or not Final answer 1mkshown) - for correct average that favour the learner within +0.1correct working of reciprocal of S.V for 1mk

ii) ½mk for evidence of reading + 0.2 of SV for ½mk- ½ for correct reading (whether shown or not)and correct working of reciprocal ii) 2mks- ½mk for evidence of reading and reading 2M x Ans (i) x 25 = Ans (ii)correctly 1000 250- ½mk for correct reading and correct working ofreciprocal iii) 1mk

c) 1mk 25 x 0.2 = 0.005Rate of reaction is directly proportional to the 1000concentration of reagents

iv) 1mkProcedure II Ans (ii) : 0.005 = correct ratioTable II 5mks distributed as follows :

v) 1mkComplete table 1mk oxidation state = +1- if all spaces are filled

2.Observations Inferences- dissolve to form colourless solution - soluble salt

- absence of Fe2+, Fe3+, Cu2+

a) No white precipitate

b) Yellow flamec) White ppt that dissolve on adding HCl d) Decolourises KMnO4 / turns acidified

KMnO4 colourless

Na+, K+, NH4+ presentPb2+, Al3+, Zn2+, Mg2+ absentNa+ present- CO 3, SO 3 present

purple SO2-3 present

3.

Observations- burns with a blue flameb)No effervesencec) - decolourises purple acidified KMnO4

d) Yellow bromine does not decolourise

Inferencessaturated organic compound - absence of H+ or R-COOH R-OH,presentR-OH present

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