10 free IGCSE Chemistry Chemical Reactions questions written in the style of Cambridge Chemistry papers: 3 multiple-choice and 7 structured, each with its answer and mark scheme. 4 of them are A* challenge questions, built to catch the mistakes strong students still make.
This topic covers Physical & chemical changes, Rate of reaction, Reversible reactions & equilibrium, Redox. Work through the questions below, then generate a full Chemical Reactions paper with a fresh set every time.
Generate a full Chemical Reactions paper →N2O4(g) ⇌ 2NO2(g) ΔH is positive.
The pressure of the equilibrium mixture is increased.
What happens to the rate of the forward reaction and to the yield of the product(s) at equilibrium?
| rate | equilibrium yield | |
|---|---|---|
| A | increases | increases |
| B | increases | decreases |
| C | decreases | increases |
| D | decreases | decreases |
Answer: B
How does a catalyst increase the rate of a reaction?
Answer: C
Why does the rate of reaction decrease as a reaction proceeds?
Answer: D
Magnesium ribbon reacts with excess dilute hydrochloric acid. The volume of hydrogen is measured every minute.
| time / min | 0 | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|---|
| volume of hydrogen / cm³ | 0 | 43 | 71 | 89 | 100 | 107 | 112 |
Calculate the average rate of reaction during the first two minutes, in cm³/min.
Describe and explain how the rate changes during the experiment. Use ideas about particles.
The experiment is repeated at a higher temperature with all other conditions the same. State the effect on the initial rate and on the total volume of hydrogen. Explain both answers.
Suggest why the total volume of hydrogen does not increase after a certain time.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 35.5 cm³/min 71 ÷ 2 M1 35.5 A1 | 2 |
| (b) | Rate decreases: the concentration of acid falls and the surface area of magnesium decreases, so there are fewer collisions per second rate decreases (as time goes on) B1 concentration of acid / amount of magnesium decreases B1 fewer (successful) collisions per second B1 | 3 |
| (c) | Initial rate is higher because particles move faster and have more energy, so more frequent and more successful collisions; total volume is the same because the same mass of magnesium (limiting) is used rate increases B1 particles have more (kinetic) energy, more frequent / more energetic collisions B1 total volume unchanged B1 same amount of the limiting reactant (magnesium) B1 | 4 |
| (d) | All the magnesium has reacted all the magnesium has been used up B1 | 1 |
Flour dust in mills can explode.
Explain why fine powders react much faster than lumps.
Suggest one way of reducing the risk of explosion.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | large surface area, more collisions a fine powder has a very large surface area B1 so there are many more collisions per second B1 | 2 |
| (b) | ventilation; no sparks good ventilation / remove dust / avoid naked flames and sparks B1 | 1 |
Zinc reacts with aqueous copper(II) sulfate: Zn + Cu²⁺ → Zn²⁺ + Cu.
Explain why this is a redox reaction, in terms of electron transfer.
State the change in oxidation number of copper.
Describe two observations.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | Zn loses electrons; Cu²⁺ gains zinc loses two electrons (oxidised) B1 copper(II) ions gain two electrons (reduced) B1 | 2 |
| (b) | +2 to 0 from +2 to 0 B1 | 1 |
| (c) | blue fades; brown/pink solid Any 2 of: blue colour fades; brown/pink solid forms (zinc dissolves; temperature rises) B2 | 2 |
A student investigates the reaction between marble chips (calcium carbonate) and dilute hydrochloric acid by measuring the volume of gas produced.
Name the apparatus used to collect and measure the gas.
Describe how the rate of reaction changes during the experiment, and explain why.
The experiment is repeated with powdered marble of the same mass. Explain why the rate is faster.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | gas syringe gas syringe (or upturned measuring cylinder over water) B1 | 1 |
| (b) | fast at start then slows as reactants used rate is fastest at the start B1 it decreases as the acid is used up/concentration falls B1 fewer collisions per second B1 | 3 |
| (c) | larger surface area, more frequent collisions powder has a larger surface area B1 more frequent collisions between particles B1 | 2 |
Oxidation and reduction can be described in several ways.
Define reduction in terms of oxygen and in terms of electrons.
In the reaction CuO + H₂ → Cu + H₂O, identify the oxidising agent.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | loss of oxygen; gain of electrons loss of oxygen B1 gain of electrons B1 | 2 |
| (b) | copper(II) oxide copper(II) oxide B1 | 1 |
A student investigates the effect of concentration on the reaction between magnesium ribbon and hydrochloric acid.
State two variables that must be kept constant.
Explain, using collision theory, why a more concentrated acid reacts faster.
Suggest one hazard and a precaution.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | temperature; length/mass of Mg; volume of acid Any 2 of: temperature; length/mass of magnesium; volume of acid B2 | 2 |
| (b) | more particles per volume, more frequent collisions more acid particles in the same volume B1 more frequent collisions B1 | 2 |
| (c) | acid irritant; eye protection hydrochloric acid is corrosive/irritant B1 wear eye protection B1 | 2 |
Hydrated copper(II) sulfate is blue. When heated it forms white anhydrous copper(II) sulfate and water.
Write the equation for this reversible reaction.
Describe what is seen when water is added to anhydrous copper(II) sulfate.
State a use of this reaction.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | CuSO₄·5H₂O ⇌ CuSO₄ + 5H₂O correct formulae B1 reversible arrow B1 | 2 |
| (b) | white to blue, gets hot turns from white to blue B1 heat is released (it gets hot) B1 | 2 |
| (c) | test for water to test for the presence of water B1 | 1 |
In the 0620 syllabus, Chemical Reactions covers Physical & chemical changes, Rate of reaction, Reversible reactions & equilibrium, Redox.
This page has 10 Chemical Reactions questions with answers. For more, the free generator on mentorriyaz.in builds a new Chemical Reactions paper with a full mark scheme each time you click.
Riyaz Shaikh has mentored IGCSE, IB and A Level students for 15+ years, one-on-one, online and in Mumbai. The hardest questions on this site are the ones he uses to find a student's weak points.
Meet Riyaz →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