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2018 O Level Chem P1 Q11 — Stoichiometry / Mole Calculations Solution

Stoichiometry / Mole Calculations 2018 O Level Pure Chemistry · Paper 1 · Q11

Question

Sodium hydroxide reacts with sulfuric acid. The equation for the reaction is shown. 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O Which volume of 0.20 mol/dm³ sodium hydroxide reacts completely with a solution containing 0.49 g of sulfuric acid? [Mr: H₂SO₄, 98]

A12.5 cm³
B25.0 cm³
C50.0 cm³
D100.0 cm³

Correct answer: C

Video Solution

Explanation

Answer: C (50.0 cm³). The equation \(2\text{NaOH} + \text{H}_2\text{SO}_4 \rightarrow \text{Na}_2\text{SO}_4 + 2\text{H}_2\text{O}\) gives a mole ratio \(\text{NaOH} : \text{H}_2\text{SO}_4 = 2 : 1\).

Moles of \(\text{H}_2\text{SO}_4 = 0.49 / 98 = 5.00 \times 10^{-3}\) mol, so moles of \(\text{NaOH}\) needed \(= 2 \times 5.00 \times 10^{-3} = 1.00 \times 10^{-2}\) mol.

Volume \(= n / c = (1.00 \times 10^{-2}) / 0.20 = 0.0500\) dm³ \(= 50.0\) cm³. Answer C.

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