Q20Assertion & reason
Calculate the volume of 0.1 M NaOH solution required to neutralise the products formed by dissolving 1.1 g of P4O6 in H2O. (3) n+
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P4O6 + 6H2O → 4H3PO3 [H3PO3 + 2NaOH → Na2HPO3 + 2H2O] × 4 P4O6 + 8NaOH → 4Na2HPO4 + 2H2O 1mol 8 mol Product formed by 1 mol P4O6 is neutralised by 8 mol NaOH 1.1 1.1 ∴ Product formed by mol P4O6 will be neutralised by × 8 mol NaOH 220 220 Molarity of NaOH solution is 0.1M ⇒ 0.1 mol NaOH is present in 1 L solution 1.1 1.1 × 8 88 4 ∴ × 8 mol NaOH is present in L = L = L 220 220 × 0.1 220 10 = 0.4 L = 400 mL NaOH solution Distribution of marks • Correct chemical euqations (½ ×3 = 1½ mark) • Correct method of calculation (1 mark) • Correct answer (½ mark) n+