Paper 2 Chemical Reactions MCQ Practice
10 multiple-choice questions on chemical reactions for IGCSE Chemistry Paper 2. Covers rates of reaction, collision theory, catalysts, reversible reactions, and redox.
Published by IGCSEChemistry.com.my
Chemistry teaching team: K. S. Tan (15+ years teaching IGCSE Chemistry) and Ms Yash (10+ years teaching IGCSE Chemistry) and Ms Kartini (15+ years teaching IGCSE Chemistry).
Mapped to Cambridge IGCSE Chemistry 0620 (2026–2028). Last updated 2026-08-19.
Ten multiple-choice questions in the style of IGCSE Chemistry Paper 2. Choose the best answer for each, then check the mark scheme.
Question 1
Which change will increase the rate of a reaction between zinc and hydrochloric acid?
A. Using larger pieces of zinc B. Decreasing the temperature C. Using more concentrated hydrochloric acid D. Adding water to the acid
Answer
C
Increasing the concentration of hydrochloric acid means more HCl particles per unit volume. This increases the frequency of collisions between acid particles and zinc, leading to more successful collisions per second and a faster rate. Option A decreases surface area (slower), B reduces kinetic energy (slower), and D dilutes the acid (slower).
Question 2
According to collision theory, a reaction occurs when particles:
A. are close together B. collide with sufficient energy and correct orientation C. are dissolved in water D. are heated above 100 degC
Answer
B
For a reaction to occur, particles must collide with at least the activation energy and with the correct orientation. Not all collisions lead to a reaction --- only those with enough energy to break the bonds in the reactants. This is the basis of collision theory.
Question 3
Marble chips (CaCO₃) react with dilute HCl. Which graph shows the effect of using powdered CaCO₃ instead of chips, with all other conditions the same?
A. Same final volume of gas, but reached more slowly B. Greater final volume of gas, reached more quickly C. Same final volume of gas, but reached more quickly D. Smaller final volume of gas, reached more quickly
Answer
C
Powdered marble has a greater surface area than chips. More surface is exposed to the acid, so collisions happen more frequently and the reaction is faster. However, the same mass of CaCO₃ is used, so the same total amount of CO₂ is produced --- only the rate changes, not the final amount.
Question 4
A catalyst is a substance that:
A. increases the yield of a reaction B. speeds up a reaction and is used up in the process C. speeds up a reaction without being chemically changed at the end D. changes the products of a reaction
Answer
C
A catalyst increases the rate of a reaction without being chemically changed at the end of the reaction. It provides an alternative pathway with a lower activation energy. It does not change the products, the yield, or the overall energy change --- it only makes the reaction faster.
Question 5
The symbol ⇌ in an equation indicates that:
A. the reaction is very fast B. the reaction is exothermic C. the reaction is reversible D. the equation is not balanced
Answer
C
The double half-arrow symbol ⇌ indicates a reversible reaction. The forward and backward reactions can both occur. At equilibrium, the rates of the forward and backward reactions are equal, and the concentrations of reactants and products remain constant (but are not necessarily equal).
Question 6
In terms of electrons, oxidation is:
A. gain of electrons B. loss of electrons C. sharing of electrons D. transfer of protons
Answer
B
Oxidation Is Loss, Reduction Is Gain (OIL RIG). When a substance is oxidised, it loses electrons. When it is reduced, it gains electrons. In a redox reaction, one substance is oxidised (loses electrons) and another is reduced (gains electrons) --- the electrons are transferred from one to the other.
Question 7
Increasing the temperature of a reaction increases the rate because:
A. it increases the surface area of the reactants B. particles move faster with more kinetic energy, so collisions are more frequent and more energetic C. it decreases the activation energy D. it changes the products of the reaction
Answer
B
At higher temperatures, particles have more kinetic energy. They move faster, so collisions are more frequent. More importantly, a greater proportion of collisions have energy equal to or greater than the activation energy, so more collisions are successful. Temperature does not change the activation energy itself.
Question 8
In the reaction Mg + CuSO₄ → MgSO₄ + Cu, which substance is reduced?
A. Magnesium B. Copper(II) sulfate C. Magnesium sulfate D. Sulfate
Answer
B
The copper in copper(II) sulfate is reduced: Cu²⁺ + 2e⁻ → Cu. The Cu²⁺ ions gain electrons (reduction). Magnesium is oxidised: Mg → Mg²⁺ + 2e⁻ (loss of electrons). This is a displacement reaction where the more reactive metal displaces the less reactive one.
Question 9
At dynamic equilibrium in a closed system:
A. the forward and backward reactions have both stopped B. the concentrations of reactants and products are equal C. the rates of the forward and backward reactions are equal D. only the forward reaction is occurring
Answer
C
At dynamic equilibrium, both the forward and backward reactions continue to occur, but at equal rates. The concentrations of reactants and products remain constant (but not necessarily equal). The system must be closed (nothing added or removed) for equilibrium to be maintained.
Question 10
Which of the following is a redox reaction?
A. NaOH + HCl → NaCl + H₂O B. CaCO₃ → CaO + CO₂ C. 2Mg + O₂ → 2MgO D. AgNO₃ + NaCl → AgCl + NaNO₃
Answer
C
In 2Mg + O₂ → 2MgO, magnesium is oxidised (Mg → Mg²⁺, loses electrons) and oxygen is reduced (O₂ → O²⁻, gains electrons). This involves electron transfer, making it a redox reaction. Option A is neutralisation, B is thermal decomposition, and D is precipitation --- none involve electron transfer.
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