O-LevelChemistryStoichiometry5070/11 · May/June 2024 · Q101 Mark

The reactions shown all produce hydrogen. Which reaction produces the greatest volume of hydrogen, measured at room temperature and pressure?

A1.4 g carbon reacts with excess steam. C(s) + H₂O(g) → H₂(g) + CO(g)

B2.4 g calcium hydride, CaH₂, reacts with excess water. CaH₂(s) + 2H₂O(l) → Ca(OH)₂(aq) + 2H₂(g)

C4.0 g calcium reacts with excess dilute hydrochloric acid. Ca(s) + 2HCl(aq) → CaCl₂(aq) + H₂(g)

D50 cm³ of 2.0 mol/dm³ sulfuric acid reacts with excess zinc. Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)

✓ Correct answer

A: 1.4 g carbon reacts with excess steam. C(s) + H₂O(g) → H₂(g) + CO(g)

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Topic: Stoichiometry, O-Level Chemistry (syllabus 5070). Multiple choice, 1 mark.
Source: O-Level Chemistry, May/June 2024 Paper 1 Variant 1, question 10.

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