Cambridge IGCSE Chemistry - 0620 - Supplement Paper 4 2024 Summer Zone 1

1 Name the process that is used to:
(a) convert sulfur dioxide into sulfur trioxide in the manufacture of sulfuric acid
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(b) obtain water from aqueous sodium chloride
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(c) extract aluminium from purified bauxite
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(d) separate petroleum into useful substances
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(e) produce ethanol from aqueous glucose
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(f) manufacture alkenes and hydrogen from large alkane molecules
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(g) separate a mixture of soluble coloured substances.
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[Total: 7]

2 Complete Table 2.1.
Table 2.1
| atom or ion | number of protons | number of electrons | number of neutrons |
|---|---|---|---|
| $^{37}\text{Cl}$ | 17 | 17 | |
| $^{63}\text{Cu}^{+}$ | 29 | 34 | |
| | 16 | 18 | 17 |
[5]

3 This question is about the elements sodium and fluorine and the compound sodium fluoride.
(a) Sodium reacts with fluorine to form sodium fluoride.
Write a symbol equation for this reaction.
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(b) Some properties of sodium, fluorine and sodium fluoride are shown in Table 3.1.
Table 3.1
| | melting point / °C | boiling point / °C | conduction of electricity when solid | conduction of electricity in aqueous solution |
|---|---|---|---|---|
| sodium | 98 | 883 | good | |
| fluorine | -220 | -188 | poor | |
| sodium fluoride | 993 | 1695 | poor | good |
(i) Explain why sodium conducts electricity when it is a solid.
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(ii) Complete the dot-and-cross diagram in Fig. 3.1 of a molecule of fluorine.
Show outer shell electrons only.

[2]
(iii) Deduce the physical state of fluorine at -200°C. Use the data in Table 3.1 to explain your answer.
physical state ......................................................................................................................
explanation .........................................................................................................................
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[2]
(iv) Explain in terms of structure and bonding why sodium fluoride has a much higher melting point than fluorine.
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(c) Dilute aqueous sodium fluoride undergoes electrolysis.
Hydrogen is produced at the cathode.
(i) State what is meant by the term electrolysis.
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(ii) Write an ionic half-equation for the production of hydrogen at the cathode.
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[Total: 14]

4 Hydrogen iodide thermally decomposes into iodine and hydrogen. The reaction is reversible.
$2\text{HI}(g) \rightleftharpoons \text{I}_2(g) + \text{H}_2(g)$
colourless gas purple gas colourless gas
Fig. 4.1 shows a gas syringe containing a mixture of hydrogen iodide, iodine and hydrogen gases.
The gas syringe is sealed and the mixture is heated to 300°C. The mixture of gases reaches equilibrium and is purple.

(a) State what is meant by the term equilibrium.
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(b) The pressure of the mixture is increased. All other conditions stay the same. The position of equilibrium does not change.
The colour of the gaseous mixture turns darker purple.
The temperature remains constant.
(i) Explain why the position of equilibrium does not change.
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(ii) Suggest why the colour of the mixture of gases turns darker purple.
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(c) The temperature of the mixture of gases is decreased. All other conditions stay the same.
The mixture of gases turns lighter purple.
State what can be deduced about the forward reaction from this information.
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(d) Deduce the oxidation number of iodine, I, in:
HI ...............................................................................................................................................
$\text{I}_2$. ...............................................................................................................................................
[2]
(e) Methanol is manufactured by reacting carbon monoxide with hydrogen.
$\text{CO}(g) + 2\text{H}_2(g) \rightleftharpoons \text{CH}_3\text{OH}(g)$
The rate of formation of methanol increases when a catalyst is used.
(i) Choose from the list the element that is most likely to be used as the catalyst.
Draw a circle around your chosen answer.
calcium carbon copper sodium sulfur [1]
(ii) State the effect on the position of equilibrium when a catalyst is used.
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(iii) State the effect that a catalyst has on the activation energy, $E_a$, of a reaction.
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[Total: 10]

5 (a) Lead(II) bromide, $\text{PbBr}_2$, is an insoluble salt and is made by precipitation.
(i) Name two aqueous solutions that produce a precipitate of lead(II) bromide when they are mixed.
1 ..........................................................................................................................................
2 ..........................................................................................................................................
[2]
(ii) Describe how to produce a pure sample of lead(II) bromide from the mixture of aqueous solutions in (a)(i).
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(iii) Write an ionic equation for the precipitation reaction which produces lead(II) bromide. Include state symbols.
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(b) When iron(II) sulfate crystals are heated strongly, sulfur dioxide gas is given off.
Describe a test for sulfur dioxide gas.
test .............................................................................................................................................
observations ..............................................................................................................................
[2]
(c) Complete the equation for the thermal decomposition of hydrated cobalt(II) nitrate.
$2\text{Co(NO}_3)_2\cdot 4\text{H}_2\text{O} \rightarrow ....\text{CoO} + ....\text{NO}_2 + \text{O}_2 + ....\text{H}_2\text{O}$ [2]
(d) Hydrated cobalt(II) sulfate, $\text{CoSO}_4\cdot x\text{H}_2\text{O}$, produces water when it is heated.
$\text{CoSO}_4\cdot x\text{H}_2\text{O}(s) \rightarrow \text{CoSO}_4(s) + x\text{H}_2\text{O}(g)$
A student does an experiment to determine the value of $x$ in $\text{CoSO}_4\cdot x\text{H}_2\text{O}$.
step 1 The student weighs a sample of hydrated cobalt(II) sulfate.
step 2 The student heats the sample of hydrated cobalt(II) sulfate.
step 3 The student weighs the remaining solid after heating.
(i) Describe what else the student should do to ensure that all the water has been given off.
No other substances are required.
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(ii) In an experiment, 1.405g of $\text{CoSO}_4\cdot x\text{H}_2\text{O}$ is heated until all the water is given off.
The mass of $\text{CoSO}_4$ that remains is 0.775g.
$[M_r : \text{CoSO}_4, 155; \text{H}_2\text{O}, 18]$
Determine the value of x using the following steps.
● Calculate the number of moles of $\text{CoSO}_4$ that remains.
.............................. mol
● Calculate the mass of $\text{H}_2\text{O}$ given off.
.............................. g
● Calculate the number of moles of $\text{H}_2\text{O}$ given off.
.............................. mol
● Determine the value of x.
x = ..............................
[4]
[Total: 17]

6 This question is about metals.
(a) Fig. 6.1 shows a blast furnace used to extract iron from its ore.

(i) Coke and iron ore are added at the top of the blast furnace.
Name one other substance that is added at the top of the blast furnace.
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(ii) Name the substance that leaves the blast furnace at A.
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(iii) Slag is produced from an impurity in iron ore.
Name the impurity in iron ore that is converted into slag.
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(iv) Name two substances that react together to produce the high temperature in the blast furnace.
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(v) Name two waste gases that leave the blast furnace.
1 ..........................................................................................................................................
2 ..........................................................................................................................................
[2]
(b) Zinc is produced from zinc oxide in a furnace.
The zinc is produced as a gas. It then forms molten zinc.
(i) Suggest why the zinc produced inside the furnace is a gas.
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(ii) State the name of the physical change that occurs when gaseous zinc is converted into molten zinc.
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(c) Zinc is used to coat iron to prevent rusting.
(i) Name the process used to coat iron with zinc as a method of rust prevention.
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(ii) When the zinc coating is scratched, the iron underneath does not rust.
Explain why the iron underneath the zinc does not rust.
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(d) Zinc oxide neutralises both acids and bases.
(i) State the general name given to oxides that neutralise both acids and bases.
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(ii) When zinc oxide neutralises aqueous sodium hydroxide, sodium zincate is formed.
The formula of the zincate ion is $\text{ZnO}_2^{2-}$.
Deduce the formula of sodium zincate.
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(iii) Name the zinc compound that forms when zinc oxide neutralises dilute sulfuric acid.
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[Total: 14]

7 Many organic compounds contain carbon and hydrogen only.
(a) (i) Organic compound A has the following composition by mass.
C, 82.76%; H, 17.24%
Calculate the empirical formula of compound A.
empirical formula = .............................. [3]
(ii) Compound B has the empirical formula $\text{CH}_2$ and a relative molecular mass of 70.
Determine the molecular formula of compound B.
molecular formula = .............................. [1]
(b) Fig. 7.1 shows a section of polymer Q.

● Draw the displayed formula of the monomer that forms polymer Q.
● Name the monomer used to form polymer Q.
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[3]
(c) Propene, $\text{C}_3\text{H}_6$, can be produced by heating $\text{C}_{11}\text{H}_{24}$. The products of the reaction are propene, hydrogen and one other product in a 1:1:1 mole ratio.
Complete the symbol equation for this reaction.
$\text{C}_{11}\text{H}_{24} \rightarrow \text{C}_3\text{H}_6 + \text{H}_2 +$ .................. [1]
(d) Carboxylic acids and esters contain carbon, hydrogen and oxygen only.
An ester X and a carboxylic acid Y both contain 3 carbon atoms.
X and Y have the same molecular formula.
(i) State the name given to compounds with the same molecular formula but different structural formulae.
....................................................................................................................................... [1]
(ii) Esters are made by the reaction between carboxylic acids and alcohols.
Ester X is methyl ethanoate.
Name the carboxylic acid and the alcohol used to make methyl ethanoate.
carboxylic acid ....................................................................................................................
alcohol ................................................................................................................................
[2]
(iii) Draw the displayed formula of carboxylic acid Y. Name the carboxylic acid.
name ...................................................................................................................................
[2]
[Total: 13]