Paper 2 Acids and Bases MCQ Practice
10 multiple-choice questions on acids, bases, and salts for IGCSE Chemistry Paper 2. Covers pH, neutralisation, salt preparation, indicators, and oxide classification.
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
A solution has a pH of 2. Which statement is correct?
A. It is a strong alkali. B. It is a weak acid. C. It is a strong acid. D. It is neutral.
Answer
C
A pH of 2 is strongly acidic. The pH scale runs from 0 to 14: values below 7 are acidic, 7 is neutral, and values above 7 are alkaline. A pH of 2 indicates a high concentration of H⁺ ions. Note: pH alone does not distinguish strong from weak acids without knowing concentration, but at IGCSE level pH 1-2 is treated as a strong acid.
Question 2
What is the ionic equation for neutralisation?
A. Na⁺ + Cl⁻ → NaCl B. H⁺(aq) + OH⁻(aq) → H₂O(l) C. CaCO₃ → CaO + CO₂ D. Mg + 2H⁺ → Mg²⁺ + H₂
Answer
B
The ionic equation for every acid-alkali neutralisation is H⁺(aq) + OH⁻(aq) → H₂O(l). The hydrogen ion from the acid combines with the hydroxide ion from the alkali to form water. The spectator ions (such as Na⁺ and Cl⁻) are not included in the ionic equation.
Question 3
Which substance is an alkali?
A. Copper(II) oxide B. Sodium hydroxide C. Carbon dioxide D. Silicon dioxide
Answer
B
An alkali is a soluble base that produces OH⁻(aq) ions when dissolved in water. Sodium hydroxide dissolves in water to form Na⁺(aq) and OH⁻(aq). Copper(II) oxide is a base but it is insoluble, so it is not an alkali. Carbon dioxide and silicon dioxide are non-metal oxides (acidic oxides).
Question 4
What salt is produced when magnesium reacts with sulfuric acid?
A. Magnesium chloride B. Magnesium nitrate C. Magnesium sulfate D. Magnesium carbonate
Answer
C
The salt name combines the metal (magnesium) with the acid root. Sulfuric acid (H₂SO₄) produces sulfates. So the salt is magnesium sulfate: Mg + H₂SO₄ → MgSO₄ + H₂.
Question 5
An oxide reacts with both acids and bases. This oxide is described as:
A. acidic B. basic C. neutral D. amphoteric
Answer
D
An amphoteric oxide can react with both acids and bases to form a salt and water. Examples include aluminium oxide (Al₂O₃) and zinc oxide (ZnO). Acidic oxides react only with bases. Basic oxides react only with acids. Neutral oxides react with neither.
Question 6
Which colour does universal indicator turn in a solution of pH 10?
A. Red B. Green C. Blue D. Purple
Answer
C
Universal indicator turns blue at around pH 10 (moderately alkaline). The colour sequence is: red (pH 1-3), orange (pH 4), yellow (pH 5-6), green (pH 7), blue (pH 8-10), and purple/violet (pH 11-14).
Question 7
Which reaction produces a salt, water, and carbon dioxide?
A. Acid + metal B. Acid + alkali C. Acid + carbonate D. Acid + metal oxide
Answer
C
Acid + carbonate produces salt + water + carbon dioxide. For example: 2HCl + CaCO₃ → CaCl₂ + H₂O + CO₂. Acid + metal gives salt + hydrogen. Acid + alkali and acid + metal oxide both give salt + water only.
Question 8
Carbon dioxide is classified as an acidic oxide because:
A. it is produced by burning carbon B. it dissolves in water to form an acidic solution C. it is a gas at room temperature D. it reacts with acids
Answer
B
Carbon dioxide is an acidic oxide because it dissolves in water to form carbonic acid (H₂CO₃), producing an acidic solution with pH below 7. Acidic oxides are non-metal oxides that react with bases and dissolve in water to form acids. CO₂ + H₂O → H₂CO₃.
Question 9
To prepare a pure sample of copper(II) sulfate crystals from copper(II) oxide and dilute sulfuric acid, the excess copper(II) oxide is removed by:
A. evaporation B. distillation C. filtration D. chromatography
Answer
C
Excess copper(II) oxide (an insoluble black powder) is added to ensure all the acid reacts. The excess solid is then removed by filtration. The filtrate (copper(II) sulfate solution) is then heated to evaporate some water, and the remaining solution is left to crystallise.
Question 10
Which of the following is a base but not an alkali?
A. Sodium hydroxide, NaOH B. Potassium hydroxide, KOH C. Copper(II) oxide, CuO D. Hydrochloric acid, HCl
Answer
C
Copper(II) oxide is a base (it reacts with acids to form a salt and water) but it is not an alkali because it is insoluble in water and does not produce OH⁻ ions in solution. NaOH and KOH are bases that are also alkalis because they dissolve in water. HCl is an acid, not a base.
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