Chemistry · May / June 2021 · Paper 12 · Question 13

When a mixture of sodium chloride and sodium hydrogencarbonate is heated, the reaction shown takes place. 2NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g) Sodium chloride is unchanged on heating. When 6.0 g of the mixture is heated, the loss in mass is 1.5 g. What is the percentage by mass of sodium hydrogencarbonate in the mixture? [relative molecular mass, Mr: NaHCO3, 84; Na2CO3, 106; CO2, 44; H2O, 18]

1. A34%
2. B48%
3. C68%
4. D95%

As printed in the paper