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Page 1: Chemistry SPM Forecast Papers

1

1 Which of the following statements is true about a catalyst?A Increases the yield of a chemical reactionB Increases during a reactionC Lower the rate of reactionD Chemically unchanged at the end of a reaction

2 Which of the following sequences shows a decrease in the sizes of the atoms of the elements?A Hydrogen, helium, chlorineB Chlorine, iodine, heliumC Chlorine, helium, hydrogenD Iodine, hydrogen, oxygen

3 Which of the following pairs will form a covalent compound? A Lithium and chlorineB Hydrogen and chlorineC Sodium and iodineD Calcium and iodine

4 How many pairs of electrons are shared by each carbon atom in ethane?A 2 C 6B 4 D 8

5 Which substance undergoes sublimation when heated?A Chlorine C FluorineB Iodine D Bromine

6 Which substance undergoes addition reaction?A Butanoic acid C ButeneB Pentanol D Ethyl methanoate

7 Which of the following is true about pentane?A Soluble in waterB Decolourises bromine waterC Burns in air to produce CO2 and waterD Oxidised by acidified potassium manganate(VII)

solution

8 In the manufacture of sulphuric acid, the quantity of sulphur dioxide can be increased byA using vanadium(V) oxide.B decreasing the pressure.C adding more sulphur dioxide.D increasing the temperature.

9 What substances should be added to a soluble salt to determine the presence of sulphate in the salt solution?A Dilute hydrochloric acid and lead(II) nitrateB Dilute hydrochloric acidC Dilute sulphuric acid and barium chloride solutionD Dilute nitric acid and dilute silver nitrate solution

10 Which of the following is true about isomers?A They have the same physical properties.B They have the same chemical properties.C They have different molecular formulae.D They are soluble in any liquid.

11 An element has the following properties:

• Forms coloured compounds • More than one oxidation number

The element could beA a noble gas C a transition elementB a halogen D an alkali metal

12 Which of the following statements is true about the elements when moving across Period 3 of the Periodic Table?A Become less electronegativeB Increase in atomic sizeC Decrease in relative atomic massD Decrease in metallic properties

13 Which compound does not decompose when heated?A Magnesium nitrate C Potassium carbonateB Copper(II) carbonate D Ammonium nitrate

Instructions: Question 1 to Question 50 are followed by four options A, B, C and D. Choose the best option for each question and blacken the corresponding space on the objective answer sheet.

(50 marks) Time: 1 hour 15 minutes PAPER 1

CHEMISTRYSPM Forecast Paper

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14 The reaction between an alcohol and carboxylic acid will produce anA alkene C esterB alkane D alkali

15 Which of the following is an inert gas?A Oxygen C KryptonB Nitrogen D Hydrogen

16 Which of the following salts can be dissolved in water?A Silver chloride C Barium sulphateB Lead(II) sulphate D Sodium bromide

17 The diagram shows a reaction.

Palm oil Margarineprocess X

What is process X ?A Oxidation C DehydrationB Reduction D Hydrogenation

18 What is the proton number of helium?A 1 C 3B 2 D 4

19 Which of the following is true of an alkali?A Has a high concentration of H+ ionsB Has a low pH valueC Tastes bitterD Insoluble in water

20 Which alloy can be used to make the body of an airplane?A Stainless steel C BronzeB Duralumin D Titanium

21 An element X has a nucleon number of 18. What is the possible number of protons, valence

electrons and neutrons that an atom of X possess?

Number of protons

Number of valence electrons

Number of neutrons

A 8 10 8

B 8 10 6

C 6 10 8

D 10 8 8

22 The electron arrangements for X and Y are as follows:

X : 2.8.1 Y : 2.5

What is the empirical formula for the compound that is formed from X and Y ?A XY2 C X3YB X2Y D XY3

23 Which of the following reactants do not undergo a neutralisation reaction?A HNO3 + NaOHB NH3 + HClC CO + HClD H2SO4 + NaCO3

24 Which of the following will decrease the rate of reaction of the decomposition of hydrogen peroxide?A High temperatureB Addition of a catalystC Greater volume of the substanceD Low temperature

25 The diagram shows two continuous reactions.

process I

process II

CH3CH

3OH

CH2CH

2

CH2ClCH

2Cl

What is process I and process II ?A Substitution and oxidationB Addition and hydrationC Dehydration and additionD Reduction and oxidation

26 Which of the following will produce an ester?A Cl2 + CH3CHCH2

B KMnO4 + CH3CH2CH2OHC HCOOH + CH3CH2OHD C2H5COOH + Na

27 An effective collision is a collisionA with high energy.B which results in a chemical reaction.C between two reactants.D that requires a catalyst.

28 Which of the following is the same in 200 cm3 of helium gas and 200 cm3 of hydrogen gas at standard temperature and pressure?A The number of moleculesB The massC Number of protonsD Energy

29 Which of the following does not have isomers?A Methanol C PentanolB Butanol D Hexanol

30 Which of the following shows the electron arrangement of an element in Group 3 of the Periodic Table?A 2.8 C 2.8.5B 2.8.2 D 2.8.3

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31 The diagram shows an energy profile diagram of a reaction.

energy

x

R + Sy

Which of the following is true?A The reaction is exothermic.B x is the activation energy.C y will increase if a catalyst is added.D R + S are the reactants.

32 Which of the following will undergo chemical reaction with glacial ethanoic acid?A Calcium solidB Marble C Sodium hydroxide solutionD Carbon powder

33 The diagram shows the set-up of the apparatus of an experiment.

iron spooncopperrod

copper(II) sulphatesolution

Which of the following is a false observation?A The intensity of the blue solution is unchanged.B The copper rod becomes thinner.C The spoon becomes thicker.D The concentration of sulphate ions increases.

34 The diagram shows the set-up of apparatus of an experiment.

crucibleheat

steam

MgO powder

Which of the following statements is true about the experiment?A Steam is oxidised by magnesium.B MgO powder increases in mass.C CO2 is formed.D White solid is formed.

35 What happens during the change of state of matter from liquid to gas?A The release of energy.B The decrease in kinetic energy.C Spaces between the particles become smaller.D The particles move more randomly.

36 Which of the following substances is sensitive to light?A Silver chloride B Silver carbonate C Sodium chlorideD Copper nitrate

37 Which of the following is true about an ionic compound?A It is insoluble in water.B It has a high melting point.C It is a good heat insulator.D It is very hard.

38 Which information is not needed to determine the heat of neutralisation between a dilute acid and a dilute alkali?A Specific heat capacity of the solutionsB Total volume of the mixtureC Initial and final temperatures of the solutionsD Temperature of the container used

39 Which of the following will not produce Pb2+ ions?A Electrolysing molten lead(II) bromideB Heating lead(II) oxide with carbonC Adding zinc powder to lead(II) nitrate solutionD Passing chlorine gas over heated lead(II)

chloride

40 Most traditional medicine can be obtained from plants.

Which of the following is a traditional medicine?A Streptomycin B Ascorbic acid C Quinine D Insulin

41 The diagram shows the set-up of the apparatus of an experiment.

copper plate

silver nitrate solution

What can be observed from the experiment?A A green solution is formed.B A gas is evolved.C A blue solution is formed.D A brown precipitate is formed.

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42 The diagram shows the set-up of the apparatus of an experiment.

magnesium ribbon

nitric acid solution

Which of the following is true about the experiment?A A catalyst must be used.B The concentration of nitric acid decreases.C Mg ribbon remains in the solution.D No gas is given off.

43 The diagram shows the set-up of the apparatus of an experiment.

litmussolution

gas X

The litmus solution turns blue. What is gas X?

A Oxygen B Ammonia C Helium D Nitrogen

44 The electron arrangement of an atom of element P is 2.8.8.2. Which of the following is true about this element?A It is in Group 3 of the Periodic Table.B It is a halogen.C It is a metal.D It is inert.

45 Which of the following has ionic bonds?A Sulphur B Carbon dioxide C Copper(II) carbonateD Water

46 The diagram shows the set-up of the apparatus of an experiment.

V

What can be used as solutions P and Q?

Solution P Solution Q

A S(l) CH3COOH(aq)

B NaCl(l) HCl(aq)

C Zn(l) Methylbenzene

D PbI2(l) Naphthalene

47 50 cm3 of 0.5 mol dm–3 hydrochloric acid reacted completely to neutralise 0.2 mol dm–3 sodium carbonate. What is the volume of sodium carbonate used?A 50.0 cm3 C 125.5 cm3

B 62.5 cm3 D 250.0 cm3

48 The diagram shows the set-up of the apparatus of an experiment.

heated

purple

compound J +acidified potassium manganate(VII)

decolourised

What is compound J?A An acid C An alkeneB An ester D An alcohol

49 The diagram shows the set-up of the apparatus of an experiment.

acidified potassiummanganate(VII)

sulphuric acidsolution

potassiumbromide solution

V

carbon electrodecarbonelectrode R

What can be observed at carbon rod R ?

A White precipitateB Reddish-brown precipitateC Blue precipitateD Yellow precipitate

50 What is the minimum volume of oxygen gas needed to completely combust 1 mol of butane at room temperature and pressure?

[1 mol of gas occupies a volume of 24 dm3 at room temperature and pressure]A 24 dm–3 C 78 dm–3

B 48 dm–3 D 156 dm–3

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1 (a) What is the meaning of isotopes?

[1 mark]

(b) (i) Write the atomic symbol of the two isotopes of carbon.

[2 marks]

(ii) State one similarity between the isotopes in (b)(i).

[1 mark]

(iii) State one difference between the isotopes in (b)(i).

[1 mark](c) State four isotopes and their uses in daily life.

1

2

3

4 [4 marks]

2 (a) State the meaning of chemical equation.

[1 mark]

(b) (i) Complete the following chemical equation.

CuCO3heat

∆[2 marks]

(ii) Interpret the chemical equation in (b)(i) quantitatively.

[2 marks] (c) (i) Write a balanced chemical equation for the formation of ammonium chloride.

[2 marks] (ii) Interpret the chemical equation in (c)(i) qualitatively.

[2 marks]

Instructions: Answer all questions in this section. The time suggested to complete this section is 90 minutes.

Section A (60 marks) Time: 2 hour 30 minutes PAPER 2

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3 (a) State one advantage of grouping elements in the Periodic Table.

[1 mark](b) An element has the electron arrangement of 2.8.2.

(i) State the group of this element in the Periodic Table.

[1 mark]

(ii) Give the reason for your answer in (b)(i).

[1 mark]

(iii) State the period of this element in the Periodic Table.

[1 mark]

(iv) Give the reason for your answer in (b)(iii).

[1 mark]

(c) State two similarities between the elements in Group 1 of the Periodic Table.

(i)

(ii) [2 marks]

(d) State the changes in the physical properties of the elements in Group 18 when moving down the group.

[1 mark]

4 (a) State the electron arrangement of

(i) magnesium atom :

(ii) oxygen atom : [2 marks]

(b) Draw a diagram to show the formation of (i) magnesium ion (ii) oxygen ion

[3 marks]

(c) Explain the formation of the ions in (b).

[2 marks]

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(d) (i) Draw a diagram to show the ionic compound of magnesium oxide.

[3 marks] (ii) Describe the diagram in (d)(i).

[2 marks]

5 (a) Diagram 1 shows an electrolytic cell.

carbon electrodes

molten lead(II) bromide

V

heat

Diagram 1

(i) Identify the cation and anion in Diagram 1.

[2 marks] (ii) Write the half-equations for the discharge of ions at the cathode and the anode.

[2 marks](b) Diagram 2 shows a voltaic cell.

magnesiumcopper

aqueous copper(II)sulphate solution

V

Diagram 2

(i) Describe the production of electricity in Diagram 2.

[3 marks]

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(ii) Based on Diagram 2, which electrode is the anode and which is the cathode?

[2 marks] (iii) Write the half-equation for the discharge of ions at the anode.

[2 marks]

6 (a) (i) State the meaning of concentration of a solution.

[1 mark] (ii) State the meaning of the molarity of a solution.

[1 mark] (iii) Write the equation that represents the relationship between the number of moles, n, molarity, M, and

volume, V, for a solution.

[1 mark](b) Diagram 3 shows the preparation of a standard solution of 0.1 mol dm–3 sodium hydroxide, NaOH. Step I: Sodium hydroxide solution is poured into a volumetric flask.

sodium hydroxidesolution

volumetric flask

Step II: Filter funnel is rinsed several times with distilled water. More distilled water is added until the graduation mark.

distilled water

Step III: Volumetric flask is stoppered.

250 cm3 of 0.1 moldm-3 sodium hydroxidesolution

Diagram 3

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(i) What is a standard solution?

[1 mark]

(ii) State two things that should be done before Step I is performed.

1

2 [2 marks]

(iii) Why is the filter funnel rinsed several times with distilled water in Step II?

[1 mark]

(iv) Why is the volumetric flask stoppered in Step III?

[1 mark] (v) Calculate the mass of sodium hydroxide solid needed to prepare the standard 250 cm3

0.1 mol dm–3 sodium hydroxide solution. [Relative atomic mass: Na, 23; O, 16; H, 1]

[3 marks]

Section B (20 marks)Instructions: Answer one question in this section. The time suggested to complete this section is 30 minutes.

7 (a) Describe the preparation of an insoluble salt. Use diagrams to aid your description.[10 marks]

(b) Describe a test to identify the following gases. (i) Chlorine (ii) Ammonia (iii) Hydrogen chloride (iv) Sulphur dioxide (v) Nitrogen dioxide

[10 marks] 8 (a) (i) Describe the industrial process in the manufacture of ammonia. Use diagrams to aid your

description. [10 marks] (ii) Give two uses of ammonia.

[2 marks](b) State the composition and uses of brass, stainless steel and bronze.

[8 marks]

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1 Diagram 1 shows the experiments conducted to construct an electrochemical series.

Diagram 1

(a) State the hypothesis for these experiments.

[3 marks](b) Write the voltage for

(i) experiment I :

(ii) experiment II :

(iii) experiment III :

(iv) experiment IV : [3 marks]

CuSO4(aq)

Mg

Experiment I

Cu

V

CuSO4(aq)

FeCu

V

CuSO4(aq)

PbCu

V

CuSO4(aq)

ZnCu

V

0

1

23

4

5

6

Experiment II

0

1

23

4

5

6

Experiment III

0

1

23

4

5

6

Experiment IV

0

1

23

4

5

6

Section C (20 marks)Instructions: Answer one question in this section. The time suggested to complete this section is 30 minutes.

9 (a) (i) What is the meaning of the rate of reaction? Give one example of a fast reaction and one example of a slow reaction.

[3 marks] (ii) What is the meaning of activation energy? Draw an energy level diagram to show the activation energy.

[5 marks](b) Discuss four factors that may affect the rate of reaction. Give an example for each factor.

[12 marks]

10 (a) Construct a table to show the names, molecular formulae and structural formulae of the first four alcohols in the homologous series of alcohol.

[12 marks](b) Describe the industrial production of ethanol. Use diagrams to aid your description.

[8 marks]

Instructions: Answer all questions in this section. The time suggested to complete this section is 45 minutes.

(50 marks) Time: 1 hour 30 minutes PAPER 3

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(c) Construct a table to record the data obtained from these experiments.

[3 marks](d) What can be deduced from the table in (c)?

[3 marks](e) Based on the results, construct the descending sequence of these metals in the electrochemical series.

[3 marks](f) An aluminium plate is placed in Experiment I to substitute magnesium. Predict the voltage that might be

recorded.

[3 marks] (g) (i) State what will happen to the copper(II) solution at the end of the experiment.

[3 marks] (ii) Based on the observation in (c) state the operational definition of these experiments.

[3 marks](h) What inference can be made from these experiments?

[3 marks](i) State the variables in this experiment.

Manipulated variable :

Responding variable :

Constant variable :

[3 marks]

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(j) Classify the metals in these experiments based on their relative reactivity as compared to hydrogen in the electrochemical series.

[3 marks]

2 Plan an experiment to investigate how temperature may affect the rate of reaction. Your planning should include the following aspects:(a) Aim of the experiment(b) All the variables(c) Statement of hypothesis(d) List of substances and apparatus(e) Procedure of the experiment(f) Tabulation of data

[17 marks]

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ANSWERS

Paper 1 1 D 2 C 3 B 4 B 5 B 6 C 7 C 8 C 9 B 10 A 11 C 12 D 13 C 14 C 15 C 16 D 17 D 18 B 19 C 20 B 21 B 22 C 23 D 24 D 25 C 26 C 27 B 28 A 29 A 30 D 31 B 32 C 33 D 34 D 35 D36 A 37 B 38 D 39 D 40 C 41 C 42 B 43 B 44 C 45 C 46 B 47 B 48 D 49 B 50 D

PAPER 2Section A 1 (a) Isotopes are atoms of the same element with the

same proton number but different nucleon numbers.

(b) (i) 126C and 14

6C (ii) Both have the same chemical properties. (iii) They have different melting points.(c) 1 Iodine-131 is used to kill malignant cancer

cells. 2 Carbon-14 is used to determine the age of

archaeological artifacts. 3 Cobalt-60 is used for food preservation. 4 Uranium-235 is used to generate electricity.

2 (a) Chemical equation is a symbolic representation of a reaction between chemical reactants and their products. (b) (i)

CuCO3 CuO + CO2

heat

(ii) The heating of 1 mol of copper(II) carbonate produces 1 mol of copper(II) oxide and 1 mol of carbon dioxide gas.

(c) (i) NH3(aq) + HCl(aq) → NH4Cl(aq) (ii) The reaction between aqueous ammonia

solution and aqueous hydrochloric acid produces an aqueous ammonium chloride solution.

3 (a) The study of chemistry of the elements becomes easier/systematic.

(b) (i) Group 2 (ii) It has 2 valence electrons. (iii) Period 3. (iv) It has 3 shells filled with electrons. (c) (i) They are soft metals. (ii) They are good electrical conductors. (d) The melting points increase down the group.

4 (a) (i) Magnesium atom: 2.8.2 (ii) Oxygen atom: 2.6

(b) The formation of (i) magnesium ion

-2e-

2+

X

X

X

X

X

X

X X

X X

X X

X

X

X

X

X

X

X X

X X

(ii) oxygen ion

+2e-

2-

X

X

(c) A magnesium atom releases 2 electrons to produce a magnesium ion. An oxygen atom accepts 2 electrons to form an oxygen ion.

(d) (i)

Mg2+

2+X X

X

X

X X

X

XX

X

O2-

2-

X

X

(ii) The magnesium atom donates 2 electrons

to the oxygen atom in order for both to obtain the octet electron arrangement. The positively charged magnesium ion and the negatively charged oxygen ion are bonded by electrostatic force.

5 (a) (i) Cation : Lead(II) ion, Pb2+

Anion: Bromide ion, Br–

(ii) At the cathode: Pb2+ +2e– → Pb At the anode: 2Br– → Br2 + 2e–

(b) (i) Electrons from the magnesium electrode flow to the copper electrode through the external circuit and produces electric current.

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(ii) Magnesium electrode is the anode. Copper electrode is the cathode.

(iii) Mg → Mg2+ + 2e–

6 (a) (i) Concentration of a solution is the mass (g) or the number of moles of solute dissolved in a solvent to form 1 dm3 of solution.

(ii) Molarity of a solution is the concentration of a solution (g dm–3) divided by the molar mass (g mol–1).

(iii) n = M × V(b) (i) A standard solution is a solution of a

known concentration. (ii) 1 The weight of sodium hydroxide solid

must be recorded accurately. 2 The beaker used to put the sodium

hydroxide solid must be rinsed with distilled water.

(iii) To make sure that no sodium hydroxide is left on the filter funnel

(iv) To avoid evaporation of the solution M × V × RMM (v) Mass = ——————— 1000 0.1 × 250 × 40 = ——————— 1000 = 1 g

Section B 7 (a) Aqueous solution

containing the anion

Aqueous solution containing the

cation

Aqueous solution and precipitate

Filtration

Insoluble salt is obtained

Rinse with distilled water

• An insoluble salt can be prepared by precipitation.

• An insoluble salt is precipitated when the cations and anions of two aqueous solutions are mixed.

• The precipitate is then filtered • The residue is the insoluble salt.• The salt is then rinsed with distilled water to

remove impurities. [10](b) (i) Chlorine gas A greenish-yellow gas. Decolourises damp

red or blue litmus paper. (ii) Ammonia gas A colourless gas. Has a pungent smell and

turns red litmus paper to blue. Produces white precipitate with concentrated

hydrochloric acid. (iii) Hydrogen chloride A colourless gas. Has a pungent smell and

turns blue litmus paper to red. Produces white precipitate with concentrated ammonia.

(iv) Sulphur dioxide A colourless gas. Has a pungent smell and

turns blue litmus paper to red. Decolourises purple acidified potassium manganate(VII) solution.

(v) Nitrogen dioxide A brown gas. Has a pungent smell and

turns blue litmus paper to red. [10] 8 (a) (i)

Fractional distillation of

liquid air

Reaction between heated coke and

steam

Ammonia gas, NH3

Nitrogen gas, N2 (1 volume)

Hydrogen gas, H2 (3 volumes)

200 – 500 atm450 – 550 °C

• The industrial process used to manufacture ammonia is known as the Haber process.

• Nitrogen gas is obtained from the fractional distillation of liquid air.

• Hydrogen gas is obtained by reacting heated coke with steam.

• Both gases are mixed in the ratio of 1 volume nitrogen to 3 volumes hydrogen.

• The pressure used is between 200 – 500 atm.

• Iron powder is used as the catalyst.• The temperature is maintained at

450 – 550 °C.• The equation for the manufacture of

ammonia is

N2 + 3H2 ↔ 2NH3

[10] (ii) 1 Used as fertiliser. 2 Used as cooling agent in refrigerators. [2](b) Brass Composition : 70% copper & 30% zinc Use : Making kitchenware Stainless steel Composition : 74% iron, 18% chromium & 8%

nickel Use : Making cutlery Bronze Composition : 90% copper & 10% tin Use : Making ships’ propellers [8]

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Section C 9 (a) (i) Rate of reaction is the speed of a chemical

reaction. Example of a fast reaction is the

combustion of fuel. Example of a slow reaction is the rusting of

iron. [3] (ii) Activation energy is the minimum energy

required by the reactants in order to break the bonds between the molecules to produce the products in a chemical reaction.

energy

reactants

Xproducts

Key: X is the activation energy [5](b) 1 Surface area The greater the surface area, the higher the

rate of reaction. Example: 2.0 g of magnesium powder has a

greater surface area than 2.0 g of magnesium ribbon. Thus, the reaction between 2.0 g of magnesium powder with an acid solution is faster than 2.0 g of magnesium ribbon.

2 Concentration of reactants The greater the concentration of the

reactants, the higher the rate of reaction. Example: The rate of reaction between 2.0 g

of magnesium ribbon with 2.0 mol dm–3 of hydrochloric acid is higher than the rate of reaction between 2.0 g of magnesium ribbon with 1.0 mol dm–3 of hydrochloric acid.

3 Temperature of reactants The greater the temperature, the higher the

rate of reaction. Example: The rate of reaction between zinc

powder and sulphuric acid at 33 °C is greater than the rate of reaction between zinc powder and sulphuric acid at 25 °C.

4 Catalyst The presence of a catalyst may increase the

rate of reaction. Example: Manganese(IV) oxide acts a catalyst

in the decomposing process of hydrogen peroxide. [12]

10 (a)

Name Molecular formula Structural formula

Methanol CH3OH H3C-OH

Ethanol C2H5OH H3C-CH2-OH

Name Molecular formula Structural formula

Propanol C3H7OH H3C-CH2-CH2-OH

Butanol C4H9OH H3C-CH2-CH2-CH2-OH

[12](b) The industrial production of ethanol:

Crude oil

Ethene

Ethanol

catalytic cracking using Al2O3 at 600 °C

hydration with steam at 300 °C using H3PO4 as catalyst

The industrial production of ethanol involves two processes:1 The cracking of crude oil to produce ethene.2 The hydration of ethene to produce ethanol.• The cracking of crude oil is carried out at 600

°C using aluminium oxide, Al2O3 as catalyst to produce ethene.

• The ethene is reacted with steam at 300 °C using phosphoric acid, H3PO4, as the catalyst at 65 atm to produce ethanol. [8]

PAPER 3 1 (a) The further the distance between the two metals

used in the chemical cell in the electrochemical series, the higher the potential difference or the voltage. [3]

(b) (i) Experiment I: 2.50 V (ii) Experiment II: 0.70 V (iii) Experiment III: 0.30 V (iv) Experiment IV: 1.10 V [3](c)

ExperimentMetals used as the

electrodesVoltage (V)

I Copper and magnesium 2.50

II Copper and iron 0.70

III Copper and lead 0.30

IV Copper and zinc 1.10

[3](d) Magnesium has the greatest potential difference

with copper, followed by zinc, iron and lead. [3](e) Magnesium, zinc, iron, lead and copper. [3](f) Between 1.1 V and 2.5 V [3](g) (i) The intensity of the blue colour decreases.

[3] (ii) The greater the potential difference

between the copper electrode and the metal used as the other electrode, the greater the distance between the two metals in the electrochemical series. [3]

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(h) Magnesium is the most electropositive metal in the electrochemical series, followed by zinc, iron, lead and copper. [3]

(i) Manipulated variable Metals used as the negative electrode. Responding variable The voltage reading. Constant variable Copper as the positive electrode. [3]

(j) More reactive than hydrogen

Less reactive than hydrogen

Magnesium Copper

Zinc

Iron

Lead

[3] 2 (a) Aim of the experiment

To investigate how temperature may affect the rate of reaction between sodium thiosulphate and dilute sulphuric acid.

(b) All the variables Manipulated variable Temperature of sodium thiosulphate solution. Responding variable Time taken for the mark ‘X’ to disappear. Constant variables The volumes and concentrations of sodium

thiosulphate solution and sulphuric acid solution.(c) Statement of hypothesis The higher the temperature, the faster the rate

of reaction.

(d) List of substances and apparatus 50 cm3 of 0.1 mol dm–3 sodium thiosulphate

solution, 5 cm3 of 1.0 mol dm–3 sulphuric acid solution, conical flask, stopwatch, white paper with ‘X’ mark, thermometer, Bunsen burner and tripod stand.

(e) Procedure 1 50 cm3 of 0.1 mol dm–3 sodium

thiosulphate solution with a temperature of 30 °C is poured into a conical flask.

2 The conical flask is placed on a white paper marked with an ‘X’.

3 5 cm3 of 1.0 mol dm–3 sulphuric acid solution is poured quickly into the sodium thiosulphate solution.

4 The stopwatch is started immediately and the conical flask is swirled gently.

5 The time taken for the mark ‘X’ to disappear is recorded.

6 The experiment is repeated with different temperatures.

(f) Tabulation of data

Temperature of mixture

(°C)

Time taken for the mark ‘X’ to disappear (s)

Rate of reaction

(s–1)

30

40

50

60

70

[17]

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