SPM Chemistry Revision Module on the Basics

SPM CHEMISTRY

REVISION MODULE FOR THE MASTERY OF THE BASICS IN SPM CHEMISTRY

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REVISION MODULE FOR THE

MASTERY OF THE BASICS IN SPM CHEMISTRY

Panel : 1. June Ling S J SMK St Joseph, Kuching 2. Chen Soo Chien Kolej DPAH Abdilah, Kuching 3. Felix Ngui SMK Tabuan Jaya, Kuching 4. Jong Kah Yin SM Sains Kuching

Compiled and edited by : Jong Kah Yin

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INDEX

CONTENT PAGE

1 REVISION CHECK-LIST

Form 4 4 - 10

Form 5 11 - 15

2 WRITING EQUATIONS

2.1 Charges of ions 2.2 Formulae of compounds 2.3 Reactions of Acid 2.4 Displacement of Metals 2.5 Double decomposition reaction 2.6 Others

17 17

18 – 19 20 20 21

3 CALCULATIONS

3.1 Relative Masses 3.2 Mole and Number of particles 3.3 Mole and Mass & Volume of Gases 3.4 Empirical and Molecular Formulae 3.5 Calculations involving Acids and Alkali 3.6 Thermochemistry

23 24

24 – 25 26

27 – 29 29 - 30

4 GUIDED ESSAY WRITING FOR PAPER 2

4.1 Chemical Bond – Ionic bond 4.2 Chemical Bond – Covalent bond 4.3 Preparation of Salt – Insoluble salt 4.4 Preparation of Salt – Soluble salt 4.5 Rate of Reaction 4.6 Heat of Combustion

32 33 34 35

36 – 37 38 – 39

5 WRITTEN PRACTICAL PAPER - PAPER 3

5.1 Structure Questions 5.2 Essay Questions

41 – 47 48

6 SUGGESTED ANSWERS

6.1 Guided Essay for Paper 2

6.2 Written Practical Paper – Paper 3

50 – 57 58 - 64

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STUDENTS’

REVISION

CHECKLIST

FOR

SPM

CHEMISTRY

By : JONG KAH YIN SM SAINS KUCHING

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Chapter 2: The Structure of the Atom

A. Knowledge (Definition, meaning and facts) Check 1) State the kinetic theory of matter.

State one example to support the kinetic theory of matter 2) What are atom, molecule and ion?

3) What is melting point?

4) Define proton number and nucleon number.

5) State the meaning of isotopes.

6) State the uses of isotopes such as carbon-14 and cobalt-60.

B. Understanding / Application / Analysis 7) Explain why the temperature remains unchanged during the melting process.

8) Explain why the temperature remains unchanged during the freezing process.

9) A solid compound is heated until it converts into gas. Explain the changes in energy

content, forces of attraction between the particles, and arrangement of particles.

10) State the subatomic particles of an atom. Compare and contrast the relative atomic masses and the relative charges of the subatomic particles of an atom.

11) Al27

13 is the symbol of aluminium.

(a) Determine the number of neutron of aluminium. (b) Draw the electron arrangement of aluminium.

C. Synthesis (Experiment) 12) Solid Z has a melting point of 65

oC. Describe a laboratory experiment to determine the

melting point of Z. Your answer should show how the melting point of Z is determined.

13) Compound W has a freezing point of 82oC. Describe a laboratory experiment to determine

the freezing point of W.

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Chapter 3: Chemical Formulae and Equations

A. Knowledge (Definition, meaning and facts) Check 1) State the meaning of relative atomic mass based on carbon-12 scale.

2) Define mole.

3) State the meaning of molar mass

4) State the meaning of molar volume of gas.

5) State the meaning of empirical formula.

6) State the meaning of molecular formula.

B. Understanding / Application / Analysis 7) Explain why we could not determine the empirical formula of copper(II) oxide by heating

copper powder in a crucible.

8) Compare and contrast empirical formula with molecular formula using ethane as an example.

9) Vinegar is a dilute ethanoic acid with a molecular formula of CH3COOH. (a) Find the empirical formula of ethanoic acid. (b) Find the percentage composition by mass of carbon in ethanoic acid.

10) 3.6 g of carbon reacted with 0.8 g of hydrogen to form a compound. (a) Determine the empirical formula of the compound formed. (b) Given that the relative molecular mass of the compound is 88 g, find its molecular formula.

[Relative atomic mass: C ,12; H, 1] 11) Hydrogen gas is reacted with 20 g of hot copper(II) oxide powder to produce solid copper

and water. (a) Write the chemical equation for the reaction. (b) Calculate the maximum mass of solid copper formed. [Relative atomic mass: Cu, 64; O,16; H,1]

C. Synthesis (Experiment) 12) Describe a laboratory experiment to determine the empirical formula of magnesium oxide.

Your answer should include all the precautions and calculations involved. [Relative atomic mass: Mg, 24; O,16]

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Chapter 4: Periodic Table of Elements

A. Knowledge (Definition, meaning and facts) Check 1) State the basic principle of arranging the elements in the Periodic Table from its proton

number.

2) State the physical properties of Group 1.

3) State the physical properties of Group 17.

4) State the changes in the atomic size and electronegativity of elements across Period 3.

5) State three special properties of transition elements?

B. Understanding / Application / Analysis

6) State the position of element X39

20 in Periodic Table. Explain your answer.

7) When going across Period 3 from sodium to argon, the atomic size decreases. Explain.

8) When going across Period 3 from sodium to argon, the electronegativity increases. Explain.

9) The reactivity of Group 1 increases when going down the group. Explain.

10) The reactivity of Group 17 decreases when going down the group. Explain.

11) Why helium gas is not reactive?

12) X is an element from Group 1. X is burnt in oxygen and the product is dissolved in water.

What is the property of the solution formed? Explain.

13) Chlorine gas is dissolved in water. What can you observe if a piece of blue litmus paper is immersed into the solution formed? Explain.

14) W is an element from Group 1. Predict the chemical reaction of W with: a) water, b) Oxygen, State the observation and write the chemical equation involve.

C. Synthesis (Experiment)

15) Describe a laboratory experiment to compare the reactivity of elements in Group 1: lithium, sodium and potassium.

16) Describe a laboratory experiment to compare the reactivity of chlorine, bromine and iodine in the reaction with iron wool. State the observation and write the chemical equations involve in reactions.

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Chapter 5: Chemical Bonds

A. Knowledge (Definition, meaning and facts) Check 1) What is anion?

2) What is cation?

3) State two physical properties of ionic compounds.

4) State two physical properties of covalent compounds.

B. Understanding / Application / Analysis

5) Explain why sodium chloride can conduct electricity in aqueous state but cannot conduct electricity in solid state.

6) Magnesium chloride and hydrogen chloride are two compounds of chlorine. At room condition, magnesium chloride exists as a solid but hydrogen chloride exists as a gas. Explain why.

7) Describe the formation of ionic bond in sodium chloride, NaCl.

8) By using example, describe the formation of covalent bond between element from Group 14 and element from Group 17.

C. Synthesis

9) Draw electron arrangement of the compound formed from the following elements. a) Nitrogen and hydrogen, b) Carbon and oxygen, c) Magnesium and chlorine, d) Carbon and hydrogen, e) Hydrogen and chlorine, f) Sodium and oxygen.

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Chapter 6: Electrochemistry

A. Knowledge (Definition, meaning and facts) Check 1) State the meaning of electrolyte.

2) State the meaning of electrolysis.

3) State three factors affecting electrolysis of an aqueous solution.

B. Understanding / Application / Analysis 4) Explain why solution of hydrogen chloride in water can conduct electricity but solution of

hydrogen chloride in methylbenzene cannot conduct electricity.

5) By using example, explain how the following factors can determine the selective discharge of ions at the electrodes. a) Types of electrodes, b) Concentration of the ions.

6) Describe the electrolysis of molten lead(II) bromide.

7) Describe the extraction of aluminium by electrolysis.

8) Draw the structure of Daniell cell and explain how it can produce electricity.

9) Draw the structure of a dry cell and explain how it can produce electricity.

C. Synthesis 10) Describe a laboratory experiment to extract lead from lead(II) oxide by using electrolysis.

11) Describe a laboratory experiment to show that types of electrodes affect the selective

discharge of ions in electrolysis of copper(II) sulphate solution.

12) You are given magnesium ribbon, copper plate, magnesium nitrate solution, copper(II) sulphate solution, connecting wires with crocodile clips, 250 cm

3 beaker, voltmeter and

porous pot. Construct a voltaic cell by using the above materials. Explain how the voltaic cell can produce electricity. Your answer must include observation and half equations for reaction at anode and cathode.

13) Describe a laboratory experiment to construct the electrochemical series of magnesium, copper, zinc and lead.

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Chapter 7: Acids and Bases and Chapter 8: Salts

A. Knowledge (Definition, meaning and facts) Check 1) State the meaning of acid and alkali.

2) What is the meaning of strong acid and weak alkali?

3) What is neutralisation?

4) What is salt?

5) What is double decomposition reaction?

B. Understanding / Application / Analysis 6) The pH value of solution ammonia in water is 9 but the pH value of solution of ammonia in

trichlomethane is 7. Explain why the pH values of the two solutions are different.

7) 80 cm3 of distilled water is added to 20 cm

3 of 2.0 mol dm

-3 solution of HCl. Find the molarity

of the dilute solution.

8) In a titration, 40 cm3 of 0.25 mol dm

-3 potassium hydroxide, KOH solution is needed to

neutralise 20 cm3 of nitric acid, HNO3. Calculate the molarity of the nitric acid, HNO3.

9) Given dilute nitric acid and dilute sulphuric acid have the same concentration of

0.5 mol dm-3. In a neutralisation experiment, 20 cm

3 of nitric acid is required to neutralise

20 cm3 of sodium hydroxide solution but only 10 cm

3 of sulphuric acid is required to

neutralise 20 cm3 of sodium hydroxide solution. Explain why.

C. Synthesis 10) Describe a chemical test to show that a given solution is an acid.

11) Describe a laboratory experiment to determine the concentration of sodium hydroxide by

using titration process. You are given 0.2 moldm-3 of dilute sulphuric acid, phenolphthalein,

burette, pipette and conical flask.

12) You are given solid sodium chloride. Describe how you can prepare sodium chloride solution of 0.2 mol dm

-3 in laboratory by using 250 cm

3 volumetric flask.

13) Describe the preparation of zinc sulphate .

14) Describe the preparation of lead(II) chloride.

15) Describe the preparation of potassium nitrate.

16) Solid W is a salt. Describe the tests you would carry out to confirm the presence of zinc ions

and nitrate ions in the salt

17) Solid X is a metal carbonate. Beside heating, describe chemical tests that you would carry out to confirm that X consists of carbonate ions. .

18) You are given four test tubes filled with solution consisting zinc ions, lead(II) ions, aluminium ions and magnesium ions respectively. Describe the tests you would carry out to confirm the ion that is present in each test tube.

19) You are given potassium chloride solution, lead(II) oxide powder and dilute nitric acid. Describe how you would prepare lead(II) chloride salt from the given materials.

20) You are given dilute sulphuric acid, copper(II) nitrate solution and sodium carbonate solution. Describe how you would prepare copper(II) sulphate salt from the given materials.

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Chapter 9: Manufactured Substance in Industry

A. Knowledge (Definition, meaning and facts) Check 1) What is the meaning of alloy?

State the aims of making alloys. 2) What is the meaning of composite materials?

State the components of the following composite materials: a) Reinforced concrete, b) Superconductor, c) Fibre optic, d) Fibre glass, e) Photochromic glass.

3) State the catalyst, temperature and pressure of the following process: a) Contact process b) Haber process

4) What is the meaning of polymers? Name the monomer of polythene and polyvinyl chloride.

5) State four types of glass and their compositions. List the uses of each glass.

6) What is ceramics? State the properties and list the uses of ceramics.

B. Understanding / Application / Analysis 7) Bronze is an alloy consisting of copper and tin. Explain why bronze is harder than copper.

8) Explain how acid rain is formed.

Describe how acid rain causes environmental pollution.

9) Explain the industrial process involved in the manufacture of sulphuric acid. Write all the chemical equations involved.

10) Explain the industrial process involved in the manufacture of ammonia gas. Write all the chemical equations involved.

C. Synthesis 11) Describe a laboratory experiment to prepare ammonium sulphate (ammonium fertiliser)

12) Describe a laboratory experiment to compare the hardness of brass and copper.

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Chapter 10: Rate of Reaction

A. Knowledge (Definition, meaning and facts) Check 1) What is rate of reaction?

2) What is stated in the collision theory?

3) What is activation energy?

4) What is effective collision?

B. Understanding / Application / Analysis 5) Explain how total surface area (size of reactant) can increase the rate of reaction based on

collision theory.

6) Based on collision theory, explain how temperature can increase the rate of reaction.

7) Based on collision theory, explain how catalyst can increase the rate of reaction.

8) Explain why hydrochloric acid of 2.0 mol dm-3 is reacted faster with zinc compare to

hydrochloric acid of 0.5 mol dm-3 .

C. Synthesis 9) Hypothesis: The smaller the size of solid reactant, the higher the rate of reaction.

Describe a laboratory experiment to confirm the hypothesis by using the reaction between calcium carbonate and hydrochloric acid.

10) Describe a laboratory experiment to show that the presence of catalyst will increase the rate of decomposition of hydrogen peroxide.

11) Describe a laboratory experiment to show that an increase in temperature will increase the rate of reaction between sodium thiosulphate solution and sulphuric acid.

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Chapter 11: Carbon compounds

A. Knowledge (Definition, meaning and facts) Check 1) What is homologous series?

2) What is saturated hydrocarbon and unsaturated hydrocarbon? State an example of each of

them.

3) What is polymer? State an example of polymer and its monomer.

4) What are saturated and unsaturated fats?

B. Understanding / Application / Analysis 5) Explain what is isomers and isomerism by using butane as an example.

6) Explain why ethene gas can decolourises the acidified potassium mangante(II) solution

whereas ethane cannot decolourises acidified potassium mangante(II) solution.

7) Explain why both hexane and hexane having six carbon atoms per molecule but hexene burns with a more sooty flame than hexane

8) Pentane and propane are members from the alkane family. Explain why the melting point of pentane is higher than propane.

9) Propanol and propanoic acid are dissolved in water. It is found that propanol solution is a neutral but propanoic acid is an acidic solution.

10) Explain the coagulation process of latex.

11) Explain how to prevent coagulation of latex.

C. Synthesis 12) Describe a test to differential hexene and hexane.

13) Describe a laboratory experiment to prepare ethane gas from ethanol.

14) Describe a laboratory experiment to prepare ethanoic acid from ethanol.

15) Ethyl propanoate is a product from reaction between alcohol and carboxylic acid.

(a) State two physical properties of ethyl propanoate. (b) Describe a laboratory experiment to prepare ethyl propanoate. Your answer must include a diagram of the apparatus set-up and the chemical equation involved.

16) Explain how to prepare propanoic acid from propene.

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Chapter 12: Oxidation and Reduction

A. Knowledge (Definition, meaning and facts) Check 1) What is oxidation and reduction based on loss or gain of oxygen?

2) What is oxidation and reduction based on transfer of electrons?

3) What is oxidation and reduction based on changes in oxidation number?

4) What are redox reactions? State an example of redox reactions.

5) What is oxidising agent and reducing agent? State an example of oxidising agent and

reducing agent.

B. Understanding / Application / Analysis 6) Determine whether the reaction between hydrochloric acid and sodium hydroxide is a redox

reaction. Explain your answer based on changes in oxidation number.

7) Determine whether the reaction between lead(II) nitrate and copper(II) is a redox reaction. Explain your answer based on changes in oxidation number.

8) The reaction between zinc and copper(II) sulphate solution is a redox reaction. Explain.

9) When bromine water is added to the potassium iodide solution, the solution changes colour from colourless to brown. Explain the observation.

10) Describe the rusting of iron.

11) A mixture of copper(II) oxide and aluminium powder is heated strongly. The mixture burns brightly. Explain this observation based on oxidation and reduction.

12) Chlorine water is added to potassium iodide solution in a test tube. 2 cm3 of 1,1,1-

trichloroethene is added to the test tube and the mixture is shaken thoroughly. The colour of 1,1,1-trichloroethene changes from colourless to purple. Explain the observation.

C. Synthesis 13) Describe a laboratory experiment to change the oxidation number of iron from +2 to +3.

How would you confirm that iron(III) is formed?

14) Describe a laboratory experiment to change the oxidation number of iron from +3 to +2 by using zinc.

15) Describe the extraction of iron.

16) You are given lead, zinc, copper and their oxides. Describe a laboratory experiment to

compare the reactivity of these metals toward oxygen.

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Chapter 12: Thermochemistry

A. Knowledge (Definition, meaning and facts) Check 1) What is exothermic reaction and endothermic reaction?

State an example for each reaction.

2) What is heat of precipitation?

3) What is heat of displacement?

4) What is heat of neutralisation?

5) What is heat of combustion?

B. Understanding / Application / Analysis 6) Explain how exothermic reaction and endothermic are formed based on energy change

during formation and breaking of chemical bonds.

7) Explain why the heat of combustion of butanol is higher than ethanol.

8) Explain why the heat of neutralisation between strong acids and strong alkalis is a constant, that is -57kJmol

-1

9) Explain why the heat of neutralisation between ethanoic acid and sodium hydroxide is less

than -57kJmol-1

10) 50 cm

3 of 2 moldm

-3 sodium hydroxide solution is added to 50 cm

3 of 2 mol dm

-3

hydrochloric acid. The temperature increases t oC.

a) If 100 cm3 of 2 mol dm


3 of 2 mol dm

-3

hydrochloric acid, predict the increase in temperature.

b) If 50 cm3 of 1 mol dm


3 of 1 mol dm

-3


c) If 50 cm3 of 4 mol dm


3 of 4 mol dm

-3


C. Synthesis 11) Describe a laboratory experiment to determine the heat of displacement of copper by zinc.

12) Describe a laboratory experiment to determine the heat of neutralisation between strong

acids and strong alkalis.

13) Describe a laboratory experiment to determine the heat of combustion of methanol.

14) “The higher the number of carbon atoms per molecule, the higher is the heat of combustion” Describe a laboratory experiment to prove that the above statement is true by using methanol, ethanol, propan-1-ol, butan-1-ol and pentan-1-ol.

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Chapter 13: Chemicals for Consumers

A. Knowledge (Definition, meaning and facts) Check 1) What is soap?

2) What is saponification process?

3) What is detergent?

4) State the functions of each of the following additives in detergent.

a) Whitening agent(example: sodium perborate) b) Optical whitener(fluorescent dyes) c) Biological enzyme (Example: amylases, lipases, proteases and cellulases) d) Fragrance

5) What is hard water?

6) State the function of each of the following food additives:

a) Preservatives ( Sodium nitrite, sodium benzoate) b) Antioxidants (Ascorbic acid) c) Flavourings (Monosodium glutamate (MSG), Aspartame) d) Stabilisers e) Thickeners

7) State the functions of the following modern medicines.

a) Analgesics ( Aspirin, Paracetamol, Codeine) b) Antibiotics ( Penicillin, Streptomycin) c) Psychotherapeutic medicine ( Stimulant, Antidepressant, Antipsychotic)

8) State the side effects of paracetamol and aspirin.

B. Understanding / Application / Analysis 9) Describe the cleansing action of soap.

10) Explain why the cleansing action of a detergent is more effective than a soap in hard water.

C. Synthesis 11) Describe a laboratory experiment to prepare soap from palm oil using the saponification

process.

12) Describe a laboratory experiment to investigate the cleansing action of a soap and a detergent in hard water.

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2. WRITING EQUATIONS 2.1 FORMULAE OF IONS 2.2 CHEMICAL FORMULAE OF COMPOUNDS 2.3 REACTIONS OF ACIDS 2.4 DISPLACEMENT OF METALS 2.5 DOUBLE DECOMPOSITION REACTION 2.6 OTHERS

By : JONG KAH YIN SM SAINS KUCHING

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2.1 Charges of cations and anions

2.2 Formulae of compounds

Ions Formula Ions Formula

Ammonium ion NH4+ Nitrate ion NO3

-

Carbonate ion CO32- Sulphate ion SO4

2-

Sulphide ion S2- Phosphate ion PO4

3-

Sodium ion Na+ Magnesium ion Mg

2+

Oxide ion O2- Iron(II) ion Fe

2+

Aluminium ion Hydroxide ions

Bromide ion Silver ions

Lead(II) ions Calcium ion

SUBSTANCE Formula Type of

compound

Type of particles

Naphthalene C10H8 Covalent Molecules

Nitric acid HNO3 Covalent Molecules

Zinc carbonate ZnCO3 Ionic Ions

Silver chloride Ions

Magnesium Mg - Atoms

Lead(II) chloride PbCl2 Ionic Ions

Sulphur trioxide SO3 Covalent Molecules

Ammonia gas NH3 Covalent Molecules

Sulphuric acid H2SO4 Covalent Molecules

Zinc carbonate ZnCO3 Ionic Ions

Iron(II) sulphate FeSO4 Ionic Ions

Hydrogen chloride

Aluminium sulphate

Calcium hydroxide

Copper(II) nitrate

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2.3 WRITING CHEMICAL/ IONIC / HALF EQUATIONS

A. Chemical Properties of Acid

2.3.1 Metal + Acid �� Hydrogen + Salt

Example :

Chemical Equation : Fe + 2HCl � H2 + FeCl2

Ionic equations : Fe (s) + 2HCl (aq) � H2 (g) + FeCl2 (aq)

Fe + 2H + + 2 Cl

- � H2 + Fe

2+ + 2 Cl

-

Half Equations : Fe � Fe2+

+ 2e

2 H+ + 2e � H2

Applicable in topics :

a. Acid & Bases b. Preparation of Salts c. Rate of reaction

1. Nitric acid + Lead

Chemical reaction

Ionic equation

Half equations

2. Hydrochloric acid + Zinc

Chemical reaction

Ionic equation

Half equations

3. Sulphuric acid + Magnesium

Chemical reaction

Ionic equation

Half equations

4. Nitric acid + Aluminium

Chemical reaction

Ionic equation

Half equations

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2.3.2 Acid + Base �� Water + Salt

Example : H2SO4 + 2KOH � 2 H2O + K2SO4

2HNO3 + ZnO � H2O + Zn(NO3)2

Applicable in topics:

a. Acid & Bases b. Preparation of salts c. Thermochemistry

2.3.3 Acid + Metal Carbonate �� Water + Carbon dioxide + Salt

Example : 2HCl + ZnCO3 � H2O + CO2 + ZnCl2


a. Acid & Bases b. Preparation of salts and qualitative analysis of salt c. Rate of reaction

5. Hydrochloric acid + Calcium oxide

Chemical reaction

Ionic equation

6. Nitric acid + Barium hydroxide

Chemical reaction

Ionic equation

7. Sulphuric acid + Sodium hydroxide

8. Sulphuric acid + Sodium carbonate solution

Chemical reaction

Ionic equation

9. Hydrochloric acid + calcium carbonate granules

Chemical reaction

Ionic equation

10. Nitric acid + copper(II) carbonate

Chemical reaction

Ionic equation

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2.4. Displacement of metal reactions

Example : Cu(NO3)2 (aq) + Zn (s) � Cu (s) + Zn(NO3)2(aq)


1. Electrochemistry 2. Redox 3. Thermochemistry

2.5. Double decomposition

Example : AgNO3 (aq) + NaCl (aq) � AgCl (s) + NaNO3(aq)


1. Salts preparation 2. Thermochemistry

11. Silver nitrate solution + Iron metal

Chemical reaction

Ionic equation

Half equations

12. Copper(II) sulphate solution + Magnesium metal

Chemical reaction

Ionic equation

Half equations

13. Lead(II) nitrate solution + Potassium chloride solution

Chemical reaction

Ionic equation

14. Copper(II) nitrate solution + sodium carbonate solution

Chemical reaction

Ionic equation

15. Barium chloride solution + sulphuric acid

Chemical reaction

Ionic equation

16. Calcium nitrate solution + potassium sulphate solution

Chemical reaction

Ionic equation

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2.6 Others

17. Potassium iodide solution + Bromine water

Chemical reaction

Ionic equation

Half equations

18. Magnesium + chlorine gas

Chemical reaction

Half equations

19. Complete combustion of ethanol

Chemical reaction

20. Complete combustion of propene

Chemical equation

21. Heating of zinc nitrate

Chemical Equation

22. Heating of copper(II) carbonate

Chemical Equation

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3. CALCULATIONS 3.1 RELATIVE MASSES 3.2 MOLE AND NO. OF PARTICLES 3.3 MOLE AND MASS & VOLUME OF GASES 3.4 EMPIRICAL AND MOLECULAR FORMULAE 3.5 CALCULATIONS INVOLVING ACIDS & ALKALI

3.6 THERMOCHEMISTRY

By : JUNE LING S J SMK ST JOSEPH, KUCHING

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3.1 Calculate Relative Molecular Mass(Mr) or Relative Formula Mass(Mr) from Relative Atomic Mass(Ar)

Relative Atomic Mass of an element, Ar = Average mass of one atom of an element 1/12 x mass of one atom of carbon-12 Example 1 : How may times is one calcium atom heavier than one oxygen atom? [RAM O,16; Ca,40] Solution: Mass of one Ca atom 40 Mass of one O atom 16 The mass of one Ca atom is 2.5 times heavier than one oxygen atom. Example 2 : How may calcium atoms have the same mass as two atoms of bromine? [RAM Br, 80] Solution: Mass of two atoms of bromine = 2 x 80 = 160 Number of calcium atoms = 160 = 4 40

Relative Molecular Mass of a molecule, Mr, = Average mass of one molecule ______ 1/12 x mass of one atom of carbon-12

• For ionic compounds, the term Relative Formula Mass, is used in place of relative molecular mass.

• Calculate Mr by adding up all the Ar of all the atoms present in the covalent molecule or one formula unit of the ionic compound.

• Ar and Mr have no units.

Example 1 : Find the RMM and RFM of the following substances :

Molecular Substances Molecular Formula Relative Molecular Mass (RMM)

Oxygen O2 2(16) = 32

Hydrochloric acid HCl

Water H2O

Sulphuric acid H2SO4

Ammonia NH3

[Ar: S, 32; O, 16; H, 1; Cl, 35.5; N, 14]

Ionic Compounds Chemical Formula

Relative Formula Mass (RFM)

Sodium chloride NaCl 23 + 35.5 = 58.5

Aluminium oxide Al2O3

Calcium carbonate CaCO3

Hydrated Copper(II) Sulphate CuSO4.5H2O

[Ar: Na, 23; Cu, 64; Al, 27; Ca, 40; O, 16; H, 1; Cl, 35.5; S, 32]

=

= 2.5

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3.2 The Mole and the Number of Particles 1 mole = 6.02 x 10

23 number of particles.

There are three kinds of particles:

• atoms

• molecules

• ions where n = number of moles NA = Avogadro’s Constant, 6.02 x 10

23

Example 1 How many zinc atoms are there in 0.5 moles of zinc powder? Solution: The number of zinc atoms in 0.5 moles of zinc powder = 0.5 x 6.02 x 10

23

= 3.01x 1023

Example 2 (a) How many water molecules are there in a glass containing 3.5 moles of water? (b) How many hydrogen atoms are there in the glass? Solution: (a) The number of water molecules in 3.5 moles of water = 3.5 x 6.02 x 10

23

= 2.17 x 1024

(b) One molecule of water, H2O, contains two hydrogen atoms. The number of hydrogen atoms in 3.5 moles of water = 2 x 3.5 x 6.02 x 10

23

= 2 x 2.17 x 1024

= 4.21 x 1024

Example 3 (a) Find the number of moles of oxygen gas, O2, containing 3.01x 10

23 molecules of oxygen gas.

Solution: Number of particles = n x NA number of moles of oxygen gas, O2, n = Number of particles NA = 3.01x 10

23

6.02 x 1023

= 0.5 Example 4 A beaker contains 0.2 moles of MgCl2. Find the total number of ions in the beaker. Solution: 1 mole of MgCl2 gives 1mole of Mg

2+ and 2 moles of Cl

- ions i.e. 3 moles of ions in total.

Number of moles of ions in 0.2 moles of MgCl2 = 0.2 x 3 = 0.6 Number of ions = 0.6 X NA = 0.6 x 6.02 x 10

23 = 3.61 x 10

23

C) Equations for calculating the number of moles, n, in:

a) Substances n =

Number of particles = n x NA

_ m____ m= mass of a subatance Molar mass Molar mass = Ar or Mr in grams

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b) Solutions n = MV M = molarity in mol dm

-3

V = volume of the solution in dm3

When the volume of the solution is given in cm

3,

n = MV V = volume of the solution in cm

3

1000 c) Gases n = volume of a gas in dm

3

Molar volume, Vm = 22.4 dm3 at STP or 24 dm

3 at room conditions

Note: Molar Mass = mass of 1 mole of a substance in gmol

-1 = Ar or Mr in grams

Molar Volume = volume occupied by 1 mole of all gases [i.e. 22.4dm

3 at STP or 24dm

3 at room conditions]

Review Question 1: Calculating number of moles, mass in substances. Use equations in (a) above

1. Zinc, Zn Ar = 65 Calculate

a) Mass of 1 mole

b) Mass of 2 moles

c) Mass of ½ moles

d) Mass of 3.01 x 1023 Zn

atoms

2. Sodium Hydroxide, NaOH Mr = 23+16+1 = 40 a) Mass of 3 moles of NaOH:

b) Number of moles in 20g of NaOH:

3. Carbon dioxide gas, CO2 , Mr = a) Mass of 2.5 moles of CO2 gas:

b) Number of molecules in 1.5 moles of CO2 gas:

c) Number of atoms in 2 moles of CO2 gas:

4. Sodium chloride, NaCl Mr =

a) Mass of 0.65 moles :

5. Copper(II) nitrate, Cu(NO3)2 Mr = a) Number of moles in 56.4g of copper(II) nitrate

[Ar: Zn, 65; Na, 23; Cu, 64; O, 16; H, 1; C, 12; Cl, 35.5; N, 14]

Volume of a gas

Molar volume

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Example 2: Calculate the molarity of the solution obtained when 14 g of potassium hydroxide is completely dissolved in distilled water to make up 500cm

3 of solution. [Ar: K,39 H,1; O,16]

Solution: Use equation in (b) above. Number of moles of KOH, n = 14 [39+16+1] = 0.25 Example 3 Calculate the volume occupied by the following gases at STP. i) 2 moles of carbon dioxide gas ii) 16g of oxygen gas Solution: Use equation in (c) above. i) Number of moles, n = _Volume of the gas, V molar volume, Vm

Volume occupied by 2 moles of CO2, V = n x Vm

= 2 X 22.4 = 44 .8 dm

3

3.5 Using Empirical Formula to find Molecular Formula

Empirical Formula is the simplest whole number ratio of number of atoms of each element in the compound. Molecular Formula shows the actual number of atoms of each element present in a molecule of the compound. Molecular Formula = (Empirical Formula)n % composition by mass of an element in a compound = Total mass of the element in the compound Mr of the compound

Example 1: When 100grams of a hydrocarbon gas is analysed, it is found to contain 85.72% carbon and 14.28% hydrogen.

Element C H

Percentage composition by mass/%

85.72 14.28 Question gives % by mass instead of the mass of each elements in the compound.

Per 100 g 85.72 14.28 Per 100 g

Number of moles of atoms

85.72 = 7.14 12

14.28 = 14.28 1

Divide the mass of each element by its molar mass

Mole ratios 7.14 = 1 7.14

14.28 = 2 7.14

Divide each number by the smallest number

Simplest mole ratios 1 2 Get the simplest whole number ratio

Empirical Formula = CH2

Molarity of KOH, M = n x 1000 v = 0.25 x 1000 500 = 0.5 mol dm

-3

ii) n = mass of oxygen gas, O2

Mr of oxygen gas,O2

= 16 32 = 0.5 mol Volume occupied by 16g of O2 gas, v = n x 22.4 = 0.5 x 22.4 = 11.4 dm

3

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Example 2: 2.58g of a hydrocarbon contains 2.16g of carbon. The relative molecular mass of the hydrocarbon is 86. [Ar: H,1; C,12 ] Find the empirical formula and determine the molecular formula of the hydrocarbon. Solution: Step 1: Find the Empirical Formula by using the table below.

Element C H

Mass of element/g 2.16 0.42 Write down the mass of the elements as given by the question

Number of moles of atoms

2.16 = 0.18 12

0.42 = 0.42 1

Divide the mass of each element by its molar mass

Mole ratios 0.18 = 1 0.18

0.42 = 2.33 = 7 0.18 3

Divide each number by the smallest number

Simplest mole ratios 3 7 Get the simplest whole number ratio

Empirical Formula = C3H7 Step 2: Find the molecular formula of the hydrocarbon

Molecular Formula = (Empirical Formula)n = (C3H7)n

Mr = (Sum of the Ar of all atoms in the Empirical Formula) x n 86 = [ 3(12) + 7(1)] x n n = 86 = 2 43 Molecular formula : (C3H7)2 = C6H14 3.5 Calculations in Acids and alkalis

Concentration can be expressed in two ways: i) Concentration of a solution (g dm

-3) =

ii) Molarity of a solution (mol dm

-3) =

M = n V iii)Conversion between Molarity (mol dm

-3) and concentration in (g dm

-3):

x Molar Mass ÷ Molar Mass

Mass of solute in gram/g

Volume of solvent /dm3

Number of moles of solute/mol

Volume of solvent /dm3

Molarity (mol dm

-3)

Concentration (g dm

-3)

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Example 1: Calculate:- a)the molarity of a solution which is prepared by dissolving 0.5 mole of hydrogen chloride, HCl, in distilled water to make up to 250 cm

3 solution. [Ar: H,1; Cl,35.5 ]

Solution: a)From n = MV 1000 M = n x 1000 V = 0.5 x 1000 250 = 2 mol dm

-3

Example 2: Find the mass of sodium hydroxide that should be dissolved in water to produce 500cm

3

of 0.5 moldm3 sodium hydroxide solution? [Ar:H,1; Na,23; O,16]

Solution: Number of moles of NaOH, n = MV 1000 = 0.5 x 500 1000 = 0.25 Mass of 0.25 moles of NaOH = number of moles x molar mass = 0.25 x [23+16+ 1] = 0.25 x 40 = 10g Neutralisation

Neutralisation is a reaction between an acid and a base to form salt and water only. Acid A + alkali B � salt and water aA + bB � products Then, MAVA = a MBVB b

Note: Make sure that VA and VB are in the same units; both in cm

3 or both in dm

3

Example 1: 27.50cm

3 of 0.15 mol dm

-3 H2SO4 completely neutralizes 25.0 cm

3 of NaOH. Calculate the molarity

of the sodium hydroxide solution.

Solution: Step 1: Write the chemical equation for neutralization: H2SO4 + 2 NaOH � Na2SO4 + 2H2O Step 2: List down the values given by the question for each letter in the formula: MAVA = a MBVB b

MA = Molarity of acid A MB = Molarity of alkali B VA = Volume of acid A VB = Volume of alkali B a = mole ratio of acid A to alkali B b

MA = 0.15 mol dm3 MB = ?

VA = 27.50 cm3 VB = 25.0cm

3

a = 1 b 2

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Step 3: Rearrange the formula above. Substitute the values into the formula to calculate the required molarity. Molarity of NaOH, MB = b x MAVA a VB

Review Question 1: Repeat the above reaction by using 0.15 moldm

3 hydrochloric acid, HCl. Find the volume

of the acid required to completely neutralize 25.0cm3 of 0.33 mol dm

3 of NaOH solution. (Ans: 55.00cm

3; note

that HCl is a monoprotic acid whereas H2SO4 is a diprotic acid ) Preparation of a solution by dilution method

Moles of solute before dilution = moles of solute after dilution M1V1 = M2V2 Note: Make sure that V1 and V2 are of the same unit.

Example 1: Calculate the volume of 2.0 mol dm

-3 sulphuric acid, H2SO4, needed to prepare 2.5 dm

3 of 0.5 mol

dm-3 of the same acid solution.

M1V1 = M2V2 V1 = M2V2 = 0.5 x 2.5 = 0.625 dm

3 or 62.5cm

3

M1 2.0 Review questions: 1. Find the volume of 2.0 mol dm

-3 sulphuric acid, H2SO4, needed to prepare 100 cm

3 0.5 mol dm

3 sulphuric

acid. (Ans: 25cm3)

2. 200 cm

3 of 1.0 mol dm

-3 sulphuric acid, H2SO4, is poured into a 250 cm

3 volumetric flask. Distilled water is

then added to make 250 cm3 of solution. What is the molarity of the diluted acid solution?

(Ans: 0.8 mol dm-3)

3.6 Calculations in Thermochemistry Calculate:

• heat of precipitation, ∆Hppt

• heat of displacement, ∆Hdisp

• heat of neutralization, ∆Hneut (exothermic)

• heat of combustion, ∆Hcomb (exothermic)

Step 1: Write the chemical equation for the reaction Step 2: Calculate H= mcθ m= total mass of solution or water/g c = specific heat capacity of water= 4.2J g

-1 0C

-1

θ = temperature change/0C

H = heat released or absorbed in joules. Step 3 : Calculate number of moles, n, of the products formed in displacement, precipitation neutralization reactions and the number of moles of the reactant burnt in combustion. Step 4: ∆H = ___H___ Units of ∆H is in KJ mol

-1 but units for H is in J

n x 1000 Add a negative sign in front of ∆H for exothermic reaction and a positive sign in front of ∆H for endothermic reaction.

M1 = 2.0 mol dm-3 V1 = ?

M2 = 0.5 mol dm-3

V2 = 2.5 dm3

M1 = molarity of the solution before water is added V1 = volume of the solution before water is added M2 = molarity of the solution after water is added V2 = volume of the solution after water is added

= 2 x 0.15 x 27.50 1 25.0 = 0.33 mol dm

3

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Example 1: When 100cm

3 of 2.0mol dm

-3 lead(II) nitrate solution is added to 100 cm

3 of 2.0 mol dm

-3

potassium sulphate solution, the temperature of the mixture increases by 9 0C. What is the heat of

precipitation? Step 1: Write the chemical equation for the precipitation reaction:- Pb(NO3)2(aq) + K2SO4(aq) � PbSO4 (s) + 2KNO3(aq) Step 2: Calculate H= mcθ m = total mass of solution = (100+100) cm

3

= 200x4.2x 9 c = specific heat capacity of water = 4.2J g-1 0C

-1

= 7560J θ = temperature change/0C = 9

0C

Step 3 : Calculate number of moles, n, which is the same for both reacting solutions: n = MV = 2.0 x 100 = 0.2 1000 1000 Step 4 : ∆H = ___H___ n x 1000 = 7560___ 0.2 x 1000 = 37.8 kJ mol

-1

Example 2: When 30 g of butane C4H10 is completely burnt in air, the heat energy released increases the temperature of 500 cm

3 of water by 70

0C. Find the heat of combustion of butane.

Step 1:Calculate H= mcθ = 500 x 4.2 x 70 = ? J Step 2 : Calculate number of moles, n of butane. Mr [C4H10] = 4(12) + 10(1) = 58 Number of moles of butane = mass___ Molar mass = _____?_______ Step 3 : ∆H = ___H___ n x 1000 = ?______ _?_ x 1000 = ___________kJ mol

-1 (Remember to add the negative sign for exothermic reaction)

(Answer: - 284.33 kJ mol

-1)

Review Question: 50 cm

3 of 1 mol dm

-3 nitric acid is added to 50 cm

3 of 1 mol dm

-3 potassium hydroxide. The

temperature of the mixture increases by 6.5 0C. Calculate the heat of neutralization of the solution.

( Ans: - 54.6 kJ mol-1 )

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4. GUIDED ESSAY WRITING FOR PAPER 2 4.1 CHEMICAL BOND – IONIC BOND

4.2 CHEMICAL BOND – COVALENT BOND

4.3 PREPARATION OF SALT – INSOLUBLE SALT

4.4 PREPARATION OF SALT – SOLUBLE SALT

4.5 RATE OF REACTION

4.6 HEAT OF COMBUSTION

By : CHEN SOO CHIEN KOLEJ DPAH ABDILLAH, KUCHING

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4.1 CHEMICAL BONDS: IONIC BOND

Guided Exercise Exercise

1.

Element Proton number

A 3

B 9

The reaction between atoms A and B forms an ionic compound. (i) Explain how this ionic compound is formed. (ii) Draw the electron arrangement of the compound formed.

2.


C 12

D 8

The reaction between atoms C and D forms an ionic compound. (i) Explain how this ionic compound is formed. (ii) Draw the electron arrangement of the compound formed.

Answer: (i) ……….. A has electron arrangement of …….. To achieve the …………. electron arrangement // ……….. arrangement, atom A …………. one valence electron and a …………… ion, A

+ is

formed. [ A → ] ………… B has electron arrangement of ……….. To achieve the …………. electron arrangement // ………… arrangement, atom B ………….. one electron and a ……………… ion, B

- is formed.

[ B → ] A

+ and B

- ions are attracted to each other by

electrostatic forces to form an ionic compound AB. (ii)

Answer:

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4.2 CHEMICAL BONDS: COVALENT BOND


1.

Element No of protons

N 7

H 1

The reaction between nitrogen and hydrogen atoms forms a covalent compound. (i) Explain how this covalent compound is formed. (ii) Draw the electron arrangement of the compound formed.

2.

Element No of protons

C 6

Cl 17

The reaction between carbon and chlorine atoms forms a covalent compound. (i) Explain how this covalent compound is formed. (ii) Draw the electron arrangement of the compound formed.

Answer: A nitrogen ……….. has electron arrangement of …………. // A nitrogen atom has ………… valence electrons. A nitrogen atom needs ………. more electrons to achieve the …………. electron arrangement // ………… arrangement. A hydrogen …………. has electron arrangement of …………. // A hydrogen atom has …………. valence electron. Each hydrogen atom needs ……….. more electron to achieve the …………. electron arrangement // ………… arrangement. Each of the three hydrogen atoms contributes ………… electron and one nitrogen atom contributes ………… electrons for ………………. to form a covalent compound, NH3

Answer:

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4.3 PREPARATION OF SALT: INSOLBULE SALT


1. Describe the preparation of lead(II) chloride in the laboratory. In your description, include the chemical equation involved.

2. Describe the preparation of calcium sulphate in the laboratory. In your description, include the chemical equation involved.

Answer: Substances: ……………………………………solution, ……………………………………solution, ……………………. water Apparatus: …………………. cylinder, beaker, filter funnel, filter …………… Procedure: 1. ……… 50 cm

3 of ……. mol dm

-3 lead(II) nitrate

solution into a beaker. 2. Add ……… cm

3 of 1.0 mol dm

-3 sodium

chloride solution. 3. ………… the mixture with a glass rod. 4. …………. the mixture. 5. …………. the salt / precipitate with distilled water. 6. ………. the salt by pressing between pieces of filter paper. Equation: Pb(NO3)2 + NaCl → +

Answer:

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4.4 PREPARATION OF SALT: SOLUBLE SALT


1. Describe the preparation of copper(II) sulphate in the laboratory. In your description, include the chemical equation involved.

2. Describe the preparation of zinc nitrate in the laboratory. In your description, include the chemical equation involved.

Answer: Substances: ……………… acid, copper(II) ……………… // copper(II) …………….. // copper(II) ……………. powder, …………….. water Apparatus: ……………… cylinder, beaker, spatula, ……….. rod, ….……………….. dish, ………….. burner, tripod stand, wire gauze, filter …………., filter paper Procedure: 1. ……… 50 cm

3 of 1.0 mol dm

-3 sulphuric acid

into a beaker. ………… the sulphuric acid. 2. Use a spatula to add ………………… powder a little at a time into the acid. ……….. the mixture with a glass rod. 3. Continue adding copper(II) oxide until some of it no longer ……………. 4. …………. the solution into an evaporating dish to remove the unreacted copper(II) oxide. 5. ………… the solution until the final volume is 1/3 the initial volume // to produce a saturated solution. 6. ……….. the saturated solution until crystals are formed. 7. ………….. the solution to obtain the copper(II) sulphate crystals. 8. …………… the crystals with a little ………… distilled water. 9. ………….. the crystals by pressing between 2 pieces of …………… paper. Equation: CuO + H2SO4 → +

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4.5 RATE OF REACTION :


1.

Experiment I Experiment II

Reactants: 100 cm

3 of

0.5 mol dm-3 HCl,

excess CaCO3 chips

Reactants: 100 cm

3 of

1.0 mol dm-3 HCl,

excess CaCO3 chips

Compare the rate of reaction in Experiment I and II. (i) Which experiment has a higher rate of reaction? (ii) Explain your answer in (i) with reference to the collision theory.

2.


Reactants: 50 cm

3 of

1.0 mol dm-3 H2SO4 ,

excess granulated zinc

Reactants: 50 cm

3 of


excess zinc powder


Answer: (i) Rate of reaction in Experiment ……. is higher than Experiment ………… (ii) The concentration of acid / …………. ions in in Experiment II is ……….. than Experiment I. The number of H

+ ions per unit ……….. in

Experiment II is ………….. than Experiment I. Frequency of collision between ………… ions and………………..in Experiment II is ………... than in Experiment I. Frequency of……………….. collision in Experiment II is higher than in Experiment I.

Answer: (i) Rate of reaction in Experiment …….is higher than Experiment ………... (ii) In Experiment II, zinc powder has a ………… total surface area exposed to ……………….. than granulated zinc in Experiment I. Frequency of collision between ………… ions and …………….. atoms in Experiment II is …………… than in Experiment I. Frequency of……………….. collision in Experiment II is higher than in Experiment I.

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3.


Reactants: 50 cm

3 of

0.1 mol dm-3 sodium

thiosulphate solution, 5 cm

3 of 1 mol dm

-3

sulphuric acid, Temperature: 30

oC

Reactants: 50 cm

3 of

0.1 mol dm-3 sodium


3 of 1 mol dm

-3


oC


4.


Reactants: 50 cm

3 of


excess zinc powder

Reactants: 50 cm

3 of


excess zinc powder CuSO4 solution


Answer: (i) Rate of reaction in Experiment II is ………… than Experiment I. (ii) ……………… of reaction in Experiment II is higher than Experiment I …………. energy of H

+ ions and S2O3

2- ions

in Experiment II is higher than Experiment I. The H

+ ions move ………. and ………. more

often with S2O32- ions in Experiment II is

than in Experiment I. Frequency of …………….. between ………. ions and ………………. ions in Experiment II is higher than Experiment I. Frequency of …………………. collision in Experiment II is ……….. than in Experiment I. .

Answer: (i) Rate of reaction in Experiment II is …………… than Experiment I. (ii) Copper(II) sulphate solution in Experiment II acts as a …………….. whereas no catalyst is used in Experiment I In Experiment II, the presence of catalyst enables the reaction to take place through an …………… path which requires a …………. activation energy. In Experiment II, more …………….. ions and ................ atoms are able to achieve the ……………… activation energy than Experiment I. Frequency of ………………….. collision in Experiment II is ………….than in Experiment I.

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4.6 HEAT OF COMBUSTION

Describe a laboratory experiment to determine the heat of combustion of ethanol, C2H5OH. In your description, include the following: [Relative atomic mass : C=12 ; O=16 ; H=1]

o diagram showing the set-up of apparatus o procedures of the experiment o tabulation of data o calculation to obtain the heat of combustion o Two precautionary steps taken to obtain more accurate result

Answer:

Procedure:

1. Measure 100 cm3 of ………… and pour into a ………….. can. The copper can is placed

on a tripod stand. 2. Record the ………….. temperature of the water. 3. Weigh a spirit lamp with …………… and record its ………. 4. Place the spirit lamp under the ……….. can and …….… the wick of the lamp immediately. 5. …………… the water in the can continuously throughout the experiment 6. Put out the flame when the temperature of the water …………… by about 30

0C

7. Record the …………… temperature reached by the water. 8. Weigh the spirit lamp and its content ………………… and record the mass.

Tabulation of Data:

The highest temperature of …………. /

oC

T2

The initial temperature of ………… /

oC

T1

…………… of spirit lamp and its content after burning / g

m2

………….. of spirit lamp and its content before burning / g

m1

Heat of combustion is the heat change when one mole of alcohol is completely burnt in oxygen under standard conditions.

ethanol

thermometer

Copper can

water

Wooden block

Wind shield

Tripod stand

Spirit p

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Calculation steps: Increase in temperature of water = ………………

oC

Mass of ethanol burnt = ……………… g

Number of mole of C2H5OH = 46

m

= n The heat energy given out during combustion by ethanol = the heat energy absorbed by water

= mcθ = …………….. = x J

Heat of combustion of ethanol, ∆H = - mcθ J mol-1 n = ………….. J mol

-1

Two precautionary steps taken to obtain more accurate result:

1. Make sure the flame touches the ………….. of the copper can // Place the spirit lamp very close or just beneath the ………….. of the copper can.

2. Stir the water in the copper can ………………. throughout the experiment. 3. ………… the spirit lamp and its content …………………. when the flame has been put out. 4. Use a wind ………… during experiment.

[Any two]

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5. WRITTEN PRACTICAL PAPER – PAPER 3 5.1 STRUCTURE QUESTIONS

5.2 ESSAY QUESTIONS

By : FELIX NGUI SMK TABUAN JAYA , KUCHING

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Answer all the questions.

The time suggested for answering Question 1 is 45 minutes.

1 A student carried out an experiment to construct the electrochemical series by measuring

the voltage of copper and metal T in a simple voltaic cell as shown in Diagram 1.1. The

experiment is repeated by replacing metal T with metals P, Q, R and S.

DIAGRAM 1.1

The voltmeter readings for each pair of metals are shown in Diagram 1.2

DIAGRAM 1.2

(a) Based on Diagram 1.2, record the voltmeter readings for each pair of metals in Table 1.1.

Pair of metals Negative terminal Voltage / V

Cu and P P

Cu and Q Q

Cu and R Cu

Cu and S S

Cu and T Cu

TABLE 1.1

[3 marks]

Copper(II) sulphate

solution

Cu T

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(b) Based on the voltmeter readings, arrange the metals Cu, P, Q, R, S and T in descending

order of electropositivity.

_________ _________ _________ _________ _________ ________

Descending order of electropositivity of metal.

[3 marks]

(c) Complete Table 1.2 for the experiment.

Variables Action to be taken

(i) Manipulated variable:

...........................................................

...........................................................

(i) The way to manipulate variable:

.................................................................

................................................................

(ii) Responding variable:

……………………………..............

……………………………..............

(ii) What to observe in the responding

variable:

.................................................................

.................................................................

(iii) Controlled variable:

..........................................................

…………………………………......

(iii) The way to maintain the controlled

variable:

.................................................................

.................................................................

TABLE 1.2 [6 marks]

(d) State a hypothesis for this experiment.

...................................................................................................................................

...................................................................................................................................

[3 marks ]

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(e) State three observations and corresponding inferences that can be obtained from the cell

in Diagram 1.1(Cu and metal T).

Observation Inference

1 ……………………………………..

……………………………………….

……………………………………….

1 ……………………………………..

……………………………………….

……………………………………….

2 ……………………………….…….

………………………………….……

……………………………………….

2 ……………………………………..

……………………………………….

……………………………………….

3 ……………………………………..

……………………………………….

……………………………………….

3 ……………………………………..

……………………………………….

……………………………………….

[6 marks]

(f) Predict the voltage of the cells which contain the following pair of metals..

Pair of metals Voltage/ V

P and S

P and T

Q and R

[3 marks]

(g) Classify metals P, Q, R, S and T into more electropositive than copper and less

electropositive than copper. Write your answers in the table provided.

[3 marks]

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(h) Explain why the voltage of cell of copper and metal S is larger than the cell of copper and

metal P.

……………………………………………………………………………………...

……………………………………………………………………………………...

……………………………………………………………………………………...

[3 marks]

(i) Another example of a chemical cell is Daniell Cell. Draw the apparatus set-up of the

Daniell Cell of copper and metal T.

[3 marks]

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2. A student carried out an experiment to investigate the effect of concentration on the rate of

reaction. He poured 50cm3 of 0.5 mol dm

-3 sodium thiosulphate solution into a 250

cm

3 conical

flask. The conical flask was then placed on a mark “X” on a piece of white paper.

10.0 cm3 of 1.0 mol dm

-3 hydrochloric acid was added to the sodium thiosulphate solution and

shaken. At the same time, the stopwatch was started. The stopwatch was stopped as soon as

the mark “X” on the piece of white paper was no longer visible.

The student repeated the experiment using sodium thiosulphate solution with the concentration

of 1.0 mol dm-3, 1.5 mol dm

-3, 2.0 mol dm

-3 and 2.5 mol dm

-3 .

Diagram 2 shows the readings of the stopwatch for each of the reactions at different

concentrations.

(a) Record the time for each reaction in the spaces provided in Diagram 2.

[3 marks]

Diagram 2

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(b) Construct a table and record the concentration, time and

time

1 of this experiment.

[3 marks]

(c) State the operational definition for rate of reaction for this experiment.

……………………………………………………………………………………………..

……………………………………………………………………………………………..

……………………………………………………………………………………………..

[3 marks]

(d) (i) Draw a graph of concentration against

time

1on a graph paper.

[3 marks]

(ii) Using the graph drawn in (b)(i), state the relationship between concentration and the

rate of reaction.

……………………………………………………………………………………………..

……………………………………………………………………………………………..

[3 marks]

(e) Predict the time taken for the mark “X” to be no longer visible if the experiment is

repeated using 3.0 mol dm-3

sodium thiosulphate solution.

……………………………………………………………………………………………..

[3 marks]

(f) State one observation for the experiment. Explain your answer.

……………………………………………………………………………………………..

……………………………………………………………………………………………..

[3 marks]

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(g) Suggest a hypothesis for this experiment.

……………………………………………………………………………………………..

……………………………………………………………………………………………..

……………………………………………………………………………………………..

[3 marks]

(h)

Variables Action to be taken

(i) Manipulated variable:

...........................................................

...........................................................

(i) The way to manipulate variable:

......................................................................

.......................................................................

(ii) Responding variable:

……………………………...............

……………………………...............

(ii) What to observe in the responding

variable:

.......................................................................

…...................................................................

(iii) Controlled variable:

…………………………………….

……………………………………..

(iii) The way to maintain the controlled

variable:

…………………………………………….

……………………………………………..

[6 marks]

(i) The relationship between concentration and rate of reaction can be applied in our daily

life. Using your knowledge of chemistry, explain why fanning glowing charcoal will

cause the charcoal to ignite.

……………………………………………………………………………………………..

……………………………………………………………………………………………..

……………………………………………………………………………………………..

……………………………………………………………………………………………..

[3 marks]

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3.

Plan a laboratory experiment to investigate the effect of other metals on the rusting of iron.

Your planning should include the following aspects:

(a) Statement of the problem (b) All the variables

(c) Statement of the hypothesis

(d) List of substances and materials

(e) Procedure of the experiment

(f) Tabulation of data

(17 marks)

4.

Plan a laboratory experiment to compare the elasticity of vulcanised rubber and unvulcanised

rubber. Your planning should include the following aspects:






(17 marks)

5.

In an experiment to compare the effectiveness of a soap and a detergent in hard water.

Your planning should include the following aspects:






(17 marks)

“Vulcanised rubber is more elastic than unvulcanised rubber.”

“Soaps and detergents are cleansing agents but their effectiveness

in hard water is different.”

“If iron is exposed to oxygen and water, rusting will occur but if iron is in contact

with a more electropositive metal, rusting is inhibited. “

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6. SUGGESTED ANSWERS 6.1 GUIDED ESSAY WRITING FOR PAPER 2 6.2 WRITTEN PRACTICAL PAPER

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6.1 GUIDED ESSAY WRITING FOR PAPER 2

6.1.1 CHEMICAL BONDS: IONIC BOND


1.


A 3

B 9

The reaction between atoms A and B forms an ionic compound. (i) Explain how this ionic compound is formed. (ii) Draw the electron arrangement of the compound formed.

2.


C 12

D 8

The reaction between atoms C and D forms an ionic compound. (i) Explain how this ionic compound is formed. (ii) Draw the electron arrangement of the compound formed.

Answer: (i) Atom A has electron arrangement of 2.1. To achieve the stable electron arrangement // duplet arrangement, atom A donates one valence electron and a positive ion, A

+ is formed.

[ A → A+ + e ]

Atom B has electron arrangement of 2.7. To achieve the stable electron arrangement // octet arrangement, atom B receives one electron and a negative ion, B

- is formed.

[ B + e → B- ]

A

+ and B

- ions are attracted to each other by

electrostatic forces to form an ionic compound AB. (ii)

Answer: (i) Atom C has electron arrangement of 2.8.2 To achieve the stable electron arrangement // octet arrangement, atom C donates two valence electrons and a positive ion, C

2+ is formed.

[ C → C2+ + 2e ]

Atom D has electron arrangement of 2.6. To achieve the stable electron arrangement // octet arrangement, atom C receives two electrons and a negative ion, D

2- is formed.

[ D + 2e → D2- ]

C

2+ and D

2- ions are attracted to each other by

electrostatic forces to form an ionic compound CD. (ii)

A+

B -

X X

X X

X

X

X

X

X

X

X

X

+ _

C2+-

X X

X X

X

X

X

X

X

X

2+

_

D2--

X X

X X

X

X

X

X

X

X

2-

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6.1.2 CHEMICAL BONDS: COVALENT BOND


1.


N 7

H 1

The reaction between nitrogen and hydrogen atoms forms a covalent compound. (i) Explain how this covalent compound is formed (ii) Draw the electron arrangement of the compound formed.

2.


C 6

Cl 17

The reaction between carbon and chlorine atoms forms a covalent compound. (i) Explain how this covalent compound is formed (ii) Draw the electron arrangement of the compound formed.

Answer: A nitrogen atom has electron arrangement of 2.5 // A nitrogen atom has five valence electrons. A nitrogen atom needs three more electrons to achieve the stable electron arrangement // octet arrangement. A hydrogen atom has electron arrangement of 1 // A hydrogen atom has one valence electron. Each hydrogen atom needs one more electron to achieve the stable electron arrangement // octet arrangement. Each of the three hydrogen atoms contributes one electron and one nitrogen atom contributes three electrons for sharing to form a covalent compound, NH3

Answer: A carbon atom has electron arrangement of 2.4 // A carbon atom has four valence electrons. A carbon atom needs four more electrons to achieve the stable electron arrangement // octet arrangement. A chlorine atom has electron arrangement of 2.8.7 // A chlorine atom has seven valence electrons. Each chlorine atom needs one more electron to achieve the stable electron arrangement // octet arrangement. Each of the four chlorine atoms contributes one electron and one carbon atom contributes four electrons for sharing to form a covalent compound, CCl4

C

X X

X X

X

X

X

X

X

X

X X

X X

X X

X X

X

X

X

X

X

X

X

X

Cl

X X

X X

X X

X

X

X

X

X

X

X

X

Cl X

X

X X

X X

X X

X X

X

X X

X

X

X

X

X

Cl

X X

X X

X X

X

X

X

X

X

X

X

X

Cl X

X

N

X X

X X

X

X

X

X

X

X

H N

H

H

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6.1.3 PREPARATION OF SALT: INSOLBULE SALT


1. Describe the preparation of lead(II) chloride in the laboratory. In your description, include the chemical equation involved.

2. Describe the preparation of calcium sulphate in the laboratory. In your description, include the chemical equation involved.

Answer: Substances: Lead(II) nitrate solution, sodium chloride solution, distilled water Apparatus: Measuring cylinder, beaker, filter funnel, filter paper Procedure: 1. Pour 50 cm

3 of 1.0 mol dm

-3 lead(II) nitrate

solution into a beaker. 2. Add 100 cm

3 of 1.0 mol dm

-3 sodium chloride

solution. 3. Stir the mixture with a glass rod. 4. Filter the mixture. 5. Rinse / wash the salt / precipitate with distilled water. 6. Dry the salt by pressing between 2 pieces of filter paper. Equation: Pb(NO3)2 + 2NaCl → PbCl2 + 2NaNO3

Answer: Substances: Calcium nitrate solution, sodium sulphate solution, distilled water Apparatus: Measuring cylinder, beaker, filter funnel, filter paper Procedure: 1. Pour 50 cm

3 of 1.0 mol dm

-3 calcium nitrate

solution into a beaker. 2. Add 50 cm

3 of 1.0 mol dm

-3 sodium sulphate

solution. 3. Stir the mixture with a glass rod. 4. Filter the mixture. 5. Rinse / wash the salt / precipitate with distilled water. 6. Dry the salt by pressing between 2 pieces of filter paper. Equation: Ca(NO3)2 + Na2SO4 → CaSO4 + 2NaNO3

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6.1.4 PREPARATION OF SALT: SOLUBLE SALT (NOT Na

+, K+ OR NH4

+ SALT)


1. Describe the preparation of copper(II) sulphate in the laboratory. In your description, include the chemical equation involved.

2. Describe the preparation of zinc nitrate in the laboratory. In your description, include the chemical equation involved.

Answer: Substances: Sulphuric acid, copper(II) oxide // copper(II) carbonate // copper(II) hydroxide powder, distilled water Apparatus: Measuring cylinder, beaker, spatula, glass rod, evaporating dish, Bunsen burner, tripod stand, wire gauze, filter funnel, filter paper Procedure: 1. Pour 50 cm

3 of 1.0 mol dm

-3 sulphuric acid

into a beaker. Warm the sulphuric acid. 2. Use a spatula to add copper(II) oxide powder a little at a time into the acid. Stir the mixture with a glass rod. 3. Continue adding copper(II) oxide until some of it no longer dissolves. 4. Filter the solution into an evaporating dish to remove the unreacted copper(II) oxide. 5. Heat the solution until the final volume is 1/3 the initial volume // to produce a saturated solution. 6. Cool the saturated solution until crystals are formed. 7. Filter the solution to obtain the copper(II) sulphate crystals. 8. Rinse the crystals with a little cold distilled water. 9. Dry the crystals by pressing between 2 pieces of filter paper. Equation: CuO + H2SO4 → CuSO4 + H2O

Answer: Substances: Nitric acid, zinc // zinc oxide // zinc carbonate // zinc hydroxide powder, distilled water Apparatus: Measuring cylinder, beaker, spatula, glass rod, evaporating dish, Bunsen burner, tripod stand, wire gauze, filter funnel, filter paper Procedure: 1. Pour 50 cm

3 of 1.0 mol dm

-3 nitric acid

into a beaker. Warm the nitric acid. 2. Use a spatula to add zinc oxide powder a little at a time into the acid. Stir the mixture with a glass rod. 3. Continue adding zinc oxide until some of it no longer dissolves. 4. Filter the solution into an evaporating dish to remove the unreacted zinc oxide. 5. Heat the solution until the final volume is 1/3 the initial volume // to produce a saturated solution. 6. Cool the saturated solution until crystals are formed. 7. Filter the solution to obtain the zinc nitrate crystals. 8. Rinse the crystals with a little cold distilled water. 9. Dry the crystals by pressing between 2 pieces of filter paper. Equation: ZnO + 2HNO3 → Zn(NO3)2 + H2O

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6.1.5 RATE OF REACTION :


1.


Reactants: 100 cm

3 of

0.5 mol dm-3 HCl,

excess CaCO3 chips

Reactants: 100 cm

3 of

1.0 mol dm-3 HCl,

excess CaCO3 chips


2.


Reactants: 50 cm

3 of


excess granulated zinc

Reactants: 50 cm

3 of


excess zinc powder


Answer: (i) Rate of reaction in Experiment II is higher than Experiment I. (ii) The concentration of acid / hydrogen ions in in Experiment II is higher than Experiment I. The number of H

+ ions per unit volume in

Experiment II is higher than Experiment I. Frequency of collision between H

+ ions and

CaCO3 in Experiment II is higher than in Experiment I. Frequency of effective collision in Experiment II is higher than in Experiment I.

Answer: (i) Rate of reaction in Experiment II is higher than Experiment I. (ii) In Experiment II, zinc powder has a larger total surface area exposed to collision than granulated zinc in Experiment I. Frequency of collision between H

+ ions and

zinc atoms in Experiment II is higher than in Experiment I. Frequency of effective collision in Experiment II is higher than in Experiment I.

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3.


Reactants: 50 cm

3 of

0.1 mol dm-3 sodium


3 of 1 mol dm

-3


oC

Reactants: 50 cm

3 of

0.1 mol dm-3 sodium


3 of 1 mol dm

-3


oC


4.


Substances: 50 cm

3 of


excess zinc powder

Substances: 50 cm

3 of


excess zinc powder, CuSO4 solution


Answer: (i) Rate of reaction in Experiment II is higher than Experiment I. (ii) Temperature of reaction in Experiment II is higher than Experiment I Kinetic energy of H

+ ions and S2O3

2- ions in

Experiment II is higher than Experiment I. The H

+ ions move faster and collide more

often with S2O32- ions in Experiment II is

than in Experiment I. Frequency of collision between H

+ ions and

S2O32- ions in Experiment II is higher than in

Experiment I. Frequency of effective collision in Experiment II is higher than in Experiment I.

Answer: (i) Rate of reaction in Experiment II is higher than Experiment I. (ii) Copper(II) sulphate solution in Experiment II acts as a catalyst whereas no catalyst is used in Experiment I In Experiment II, the presence of catalyst enables the reaction to take place through an alternative path which requires a lower activation energy. In Experiment II, more H

+ ions and zinc

atoms are able to achieve the lower activation energy than Experiment I. Frequency of effective collision in Experiment II is higher than in Experiment I.

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6.1.6 HEAT OF COMBUSTION

Describe a laboratory experiment to determine the heat of combustion of ethanol, C2H5OH. In your description, include the following: [Relative atomic mass : C=12 ; O=16 ; H=1]

o diagram showing the set-up of apparatus o procedures of the experiment o tabulation of data o calculation to obtain the heat of combustion o Two precautionary steps taken to obtain more accurate result

Answer:

Pipe clay triangle Spirit lamp

Procedure:

1. Measure 100 cm3 of water and pour into a copper can. The copper can is placed on a

tripod stand. 2. Record the initial temperature of the water. 3. Weigh a spirit lamp with ethanol and record its mass. 4. Place the spirit lamp under the copper can and light the wick of the lamp immediately. 5. Stir the water in the can continuously throughout the experiment. 6. Put out the flame when the temperature of the water increases by about 30

0C.

7. Record the highest temperature reached by the water. 8. Weigh the spirit lamp and its content immediately and record the mass.

Tabulation of Data:

The highest temperature of water /

oC

T2

The initial temperature of water /

oC

T1

Mass of spirit lamp and its content after burning / g

m2

Mass of spirit lamp and its contents before burning / g

m1

Heat of combustion is the heat change when one mole of alcohol is completely burnt in oxygen under standard conditions.

ethanol

Thermometer

Copper can

water

Wooden block

Wind shield

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Calculation steps: Increase in temperature of water = (T2 - T1)

oC

Mass of ethanol burnt = (m1 - m2) g

Number of mole of C2H5OH = 46

m

= n The heat energy given out during combustion by ethanol = the heat energy absorbed by water

= mcθ = mc(T2-T1) = x J

Heat of combustion of ethanol, ∆H = - mcθ J mol-1 n = - x J mol

-1

n Two precautionary steps taken to obtain more accurate results:

1. Make sure the flame touches the base of the copper can // Place the spirit lamp very close or just beneath the base of the copper can. 2. Stir the water in the copper can continuously throughout the experiment. 3. Weigh the spirit lamp and its content immediately when the flame has been put out. 4. Use a wind shield during experiment.

[Any two]

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6.2 MARKING SCHEME CHEMISTRY PAPER 3

Question Rubric Score

1(a) [Able to record all the five readings accurately]:

Suggested answer:

Pairs of electrodes Voltage/V

Cu and P 1.5

Cu and Q 1.7

Cu and R 0.5

Cu and S 2.3

Cu and T 1.2

3

1 (b) [Able to arrange the position of all metals in descending order of

electropositivity correctly]

Suggested answer:

S, Q, P, Cu, R, T

3

1 (c)

[Able to state three variables and the way to control them correctly]

Suggested answer:

Manipulated variable:

Pair of metals

Substituting the electrode T with

different metals //

P, Q, R, S and T

Responding variable:

Voltmeter reading

Reading of the voltmeter//

voltage

Controlled variable:

Electrolyte / copper(II) sulphate

solution // concentration and

volume of electrolyte //

same voltmeter //

copper electrode

Use the same electrolyte /

concentration of electrolyte /

CuSO4 //

use the same voltmeter //

use copper electrode in all

experiments.

6

1 (d) [Able to state the relationship between the manipulated variable and the

responding variable and the direction correctly]

Suggested answer:

The further apart / the distance of the pair of metals in the electrochemical

series, the higher is the voltage / the voltmeter reading.

3

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Question Explanation Maximum

score

1(e)

[Able to state three observations and three inferences correctly]

Observation Inference

1. Copper strip / rod / metal

dissolves / becomes thinner

Copper is oxidised / loses electron

to form copper(II) ion // Copper is

more electropositive than P.

2. Brown solid is deposited at

metal T

Copper is formed // Cu2+ is reduced

to copper

3. The intensity of the blue

coloured solution remains

unchanged

The concentration of Cu2+ in the

solution remain unchanged // the

rate of Cu2+ formed at anode is the

same as the rate of discharge of

Cu2+ at the cathode.

6

1(f)

[Able to predict the voltage of the three cells accurately]

Suggested answer:

Pair of metals Voltage/ V

P and S 0.8

P and T 2.7

Q and R 2.4

3

1(g)

[Able to classify all the metals correctly]

Suggested answer:

More electropositive Less electropositive

P, Q, S R, T

3

1(h) [Able to explain the difference in the voltage of the cell]

Suggested answer:

The distance between Cu and metal S is further / greater than the distance

between Cu and metal P in the electrochemical series.

3

1(i)

[Able to draw the labeled apparatus set-up completely]

Suggested answer:

3

Copper Metal T

Copper(II)

sulphate

solution

T nitrate

solution

Salt bridge

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2 (a) [Able to record all the five readings accurately to one decimal point]:

t1 = 55.0 s, t2 = 48.0 s, t3 = 42.0 s, t4 = 37.0 s, t5 = 33.0 s, 3

(b) [Able to construct a table and transfer all the five readings from (a) correctly

with unit for each heading.. The values for time

1 must be given to three

decimal places].

Concentration /

mol dm-3

Time / s

time

1 / s

-1

0.5 55.0 0.018

1.0 48.0 0.021

1.5 42.0 0.024

2.0 37.0 0.027

2.5 33.0 0.030

3

(c) [Able to give the operational definition correctly]

Rate of reaction is inversely proportional to the time taken for the mark

“X” to be no longer visible // Rate of reaction ∝ time

1

3

(d) [ Able to do the following:

• Draw a graph of suitable size / using suitable scale (occupying about

75% of graph paper)

• Label the axes concentration / mol dm-3 and time

1/ s

-1

• Plot the five points correctly from the table constructed in (b)

• Draw a straight line (linear) graph ]

(i) concentration / mol dm-3

0.09

0.08

0.07

0.06

0.05

0.04

0.03

0.02

0.01

0 time

1/ s

-1

0.01 0.02 0.03 0.04 0.05

3

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(d) [ Able to state the relationship between concentration and the

rate of reaction correctly]

(ii) An increase in concentration (of sodium thiosulphate solution) will

increase the rate of reaction.

3

(e) [Able to predict the time taken using the graph drawn]

Suggested answer : 30 s

3

(f) [Able to state and explain the observation correctly.]

A yellow precipitate is formed.

The reaction of hydrochloric acid and sodium thiosulphate solution produces

sulphur, sulphur dioxide and water. // The sulphur produced from the reaction

forms the yellow precipitate.

3

(g) [Able to state the relationship between the manipulated variable and the

responding variable and the direction correctly]

The higher / lower the concentration of sodium thiosulphate solution, the

shorter / longer the time taken for the mark “X” to be no longer visible.

3

(h)

[Able to state three variables and the way to control them correctly]

Suggested answer:

Manipulated variable:

Concentration of sodium

thiosulphate solution

Repeat the experiment using

sodium thiosulphate solution with

concentrations of 1.0 mol dm-3,

1.5 mol dm-3, 2.0 mol dm

-3 and

2.5 mol dm-3 .

Responding variable:

Time taken for the mark

“X” to be no longer visible //

Rate of reaction

Time taken for the mark “X” to be

no longer visible

Controlled variable:

Temperature of sodium

thiosulphate solution // size of

conical flask // concentration and

volume of hydrochloric acid used

// total volume of reacting

mixture

Reject : Use of “Quantity” or

“amount of “ hydrochloric acid /

reacting mixture.

Solutions of same temperature are

used // use conical flasks of same

size // use the same concentration

and volume of hydrochloric acid //

keep the total volume of reacting

mixture the same.

6

(i) [Able to explain phenomena using relevant knowledge of chemistry] Suggested answer :

Fanning increases the concentration of oxygen blown over glowing charcoal //

Fanning causes the glowing charcoal to be exposed to more oxygen.

Thus, the glowing charcoal ignites.

3

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3(a) How do different metals in contact with iron affect the rusting of iron? // What

is the effect of different metals in contact with iron on the rusting of iron nails

?

3

(b) Iron nail rusts when it is in contact with a less electropositive metal. Iron nail

does not rust when it is in contact with a more electropositive metal 3

(c) MV : Different metals in contact with iron nail

RV: Rusting of iron

CV: Type of (iron) nail, medium in which iron nail is kept, temperature

3

(d) Name one metal more electropositive (magnesium) than iron and one metal

less electropositive (copper) than iron.

Materials : Iron nails, magnesium ribbon, copper foil, hot jelly solution

containing potassium hexacyanoferrate(III) solution, sandpaper.

Apparatus : test tubes, test tube rack,

3

(e) Procedure :

1. Clean / Rub three iron nails with sandpaper.

2. Two iron nails are coiled / wound separately with magnesium ribbon

and copper foil.

3. The three nails are each put / dip / immersed into labelled test tubes

A, B and C containing hot jelly solution with potassium

hexacyanoferrate(III) solution separately .

4. The test tubes are put on a test tube rack under room condition for a

few days.

5. The test tubes are observed and the results are recorded.

3

(f) Tabulation of data : Suggested answer(any one )

Pair of metal Observation

Iron nail only

Iron nail coiled with

magnesium ribbon

Iron nail coiled with

copper foil

Tets tube Pair of metal Observation

A Iron nail only

B Iron nail coiled with

magnesium ribbon

C Iron nail coiled with

copper foil

3

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4 (a) Is vulcanised rubber more elastic than unvulcanised rubber ? //

How does the elasticity of vulcanised rubber differ from unvulcanised

rubber ? //

Does vulcanisation increase the elasticity of rubber?

3

(b) MV : Types of rubber // Vulcanised and unvulcanised rubber

RV: Length of rubber strip

CV : Size of rubber strip, mass of weight

3

(c) Vulcanised / Unvulcanised rubber is more elastic than unvulcanised /

vulcanised rubber. 3

(d) Materials : Vulcanised rubber strip, unvulcanised rubber strip

Apparatus: Retort stand and clamp, (bulldog) clips, ruler, 10 g, 20 g,

30 g , 40 g and 50 g weights,

3

(e) Procedure :

1. (Using bulldog clips,) hang a vulcanised rubber strip and an

unvulcanised rubber strip onto a retort stand each.

2. The (initial) lengths of the two rubber strips are measured.

3. A 10 g weight is hung to each of the two strips and the lengths of the

two strips are measured and recorded.

4. The weights are removed and the lengths of the rubber strips are

measured and recorded.

5. Steps 3 and 4 are repeated using 20g, 30g, 40g and 50g weights to

replace the 10 g weights.

3

(f)

Tabulation of data

Weights

/ g

Length of vulcanised rubber

strip / cm

Length of unvulcanised

rubber strip / cm

Without

weight

With

weight

Weight

removed

Without

weight

With

weight

Weight

removed

10

20

30

40

50

3

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5(a) How effective are // How is the effectiveness of soaps and detergents in

hard water ? //

What is the effectiveness of soaps and detergents in hard water ? //

Is the cleansing action of a detergent / soap more effective than that of a

soap / detergent in hard water ? //

Is soap as effective as detergent in hard water ?

3

(b) Detergents are effective in hard water. Soaps are less / not effective in

hard water. //

Detergent is a more effective cleansing agent than soap in hard water.

3

(c) MV : Different types of cleansing agent / Detergent and soap

RV: (Removal of) oily stain on a cloth

CV: Volume and concentration of magnesium sulphate solution, volume

and concentration of detergent and soap, type of stain / oil stain on

cloth, temperature of magnesium sulphate // calcium sulphate

solution.

3

(d) Materials : Soap solution, detergent solution, two pieces of cloth with

oily stains, magnesium sulphate // calcium sulphate solution

Apparatus : measuring cylinder, basin // [any suitable container such as

a basin]

3

(e) Procedure :

1. 50 cm3 of 5% soap solution and 50 cm3 of 5% detergent solution are

separately poured into two beakers containing 20 cm3 of magnesium

sulphate solution / hard water.

2. A small piece of cloth with oily stains is dipped / immersed / put into

each beaker.

3. Each cloth is washed with the cleansing agent / soap or detergent in the

beaker.

4. The cleansing action of the soap and detergent is observed and

compared // The oily stain remaining on the cloth is observed and

compared.

5. The results are recorded in a table.

3

(f)

Tabulation of data :

Beaker Observation

X

Y

or

Cleansing agent Observation

Soap solution

Detergent solution

3

SPM Chemistry Revision Module on the Basics

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Transcript of SPM Chemistry Revision Module on the Basics