IGCSE · Chemistry 0620 · P4

IGCSE Chemistry Paper 4 · Theory practice papers

Extended · structured questions. Each generated paper follows the 0620 Paper 4 · Theory format, with the same number and style of questions as the real exam, and comes with a Cambridge-style mark scheme.

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Sample Paper 4 · Theory questions

Question 1Structured · 11 marksA* challenge

A student adds 5.0 g of calcium carbonate to 50 cm³ of 1.0 mol/dm³ hydrochloric acid.
CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g)

(a)

Calculate the number of moles of calcium carbonate and the number of moles of hydrochloric acid used.

[2]

(b)

Deduce which reactant is in excess. Explain your answer.

[2]

(c)

Calculate the volume of carbon dioxide, in cm³, formed at room temperature and pressure.

[2]

(d)

The solution is evaporated and 2.36 g of anhydrous calcium chloride is obtained. Calculate the percentage yield.

[3]

(e)

Suggest why the reaction becomes slower as it proceeds, in terms of particles.

[2]

Show answers and mark scheme

Part	Answer and marking points	Marks
(a)	0.05 mol, 0.05 mol 5 ÷ 100 = 0.05 B1 1 × 50 ÷ 1000 = 0.05 B1	2
(b)	calcium carbonate is in excess: 0.05 mol CaCO₃ needs 0.1 mol HCl 0.05 mol CaCO₃ reacts with 0.1 mol HCl (or 0.05 mol HCl reacts with 0.025 mol CaCO₃) M1 calcium carbonate in excess A1	2
(c)	600 cm³ moles CO₂ = 0.025 (from limiting reactant) M1 600 A1	2
(d)	85% M_r CaCl₂ = 111 B1 theoretical mass = 2.78 g M1 85 A1	3
(e)	Concentration of acid falls, so fewer particles per unit volume and collisions become less frequent concentration of (acid) particles decreases B1 fewer collisions per second / lower collision frequency B1	2

Question 2Structured · 2 marksA* challenge

Rust is hydrated iron(III) oxide.

(a)

Write a word equation for the formation of rust.

[1]

(b)

Explain why salt water speeds up rusting.

[1]

Show answers and mark scheme

Part	Answer and marking points	Marks
(a)	iron + oxygen + water → hydrated iron(III) oxide iron + oxygen + water → hydrated iron(III) oxide B1	1
(b)	electrolyte, faster the dissolved salt makes the water a better conductor (electrolyte), increasing the rate of corrosion B1	1

Question 3Structured · 5 marks

Metal displacement reactions can be used to build a reactivity series.

(a)

Describe what is seen when iron is added to copper(II) sulfate solution.

[2]

(b)

Write the ionic equation for the reaction.

[2]

(c)

Explain why silver does not react with copper(II) sulfate.

[1]

Show answers and mark scheme

Part	Answer and marking points	Marks
(a)	pink/brown solid; blue to green pink/brown copper forms on the iron B1 solution changes from blue to (pale) green B1	2
(b)	Fe + Cu²⁺ → Fe²⁺ + Cu Fe + Cu²⁺ → Fe²⁺ + Cu B2	2
(c)	silver less reactive silver is less reactive than copper B1	1

Question 4Structured · 5 marks

25.0 cm³ of sodium hydroxide solution is titrated with 0.100 mol/dm³ hydrochloric acid. The average titre is 25.00 cm³. NaOH + HCl → NaCl + H₂O

(a)

Calculate the number of moles of hydrochloric acid used.

[1]

(b)

Calculate the concentration of the sodium hydroxide in mol/dm³.

[2]

(c)

Name a suitable indicator and state the colour change at the end-point.

[2]

Show answers and mark scheme

Part	Answer and marking points	Marks
(a)	0.0025 mol 0.0025 mol B1	1
(b)	0.1 mol/dm³ moles NaOH = 0.0025 C1 ÷ 0.0250 = 0.1 mol/dm³ A1	2
(c)	methyl orange yellow → orange/red (or phenolphthalein pink → colourless) Any 2 of: methyl orange; yellow to orange (or phenolphthalein; pink to colourless) B2	2

Question 5Structured · 5 marks

Brass is an alloy of copper and zinc. Steel is an alloy of iron.

(a)

Define an alloy.

[1]

(b)

Explain, in terms of structure, why alloys are harder than pure metals.

[2]

(c)

Give a use of stainless steel and the property that makes it suitable.

[2]

Show answers and mark scheme

Part	Answer and marking points	Marks
(a)	mixture of metal with other elements a mixture of a metal with other elements (usually metals) B1	1
(b)	different sized atoms stop layers sliding different-sized atoms disrupt the regular layers B1 the layers cannot slide over each other easily B1	2
(c)	cutlery; resists corrosion cutlery/surgical instruments B1 resistant to rusting B1	2

Question 6Structured · 2 marks

Sewage treatment removes harmful substances.

Explain why untreated sewage is harmful in rivers.

[2]

Show answers and mark scheme

Part	Answer and marking points	Marks
	microbes; decomposition uses oxygen it contains pathogens B1 bacteria decomposing it use up dissolved oxygen, killing aquatic life B1	2

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States of matter Atoms, elements & compounds Stoichiometry Electrochemistry Chemical energetics Chemical reactions Acids, bases & salts The Periodic Table Metals Chemistry of the environment Organic chemistry Experimental techniques & analysis

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Original Cambridge-style practice questions written for mentorriyaz.in. These are not Cambridge past paper questions, and this site is not affiliated with or endorsed by Cambridge University Press & Assessment. Updated 2026-11-04. Paper generator · mentorriyaz.in