Chemistry 9701 · AS & A Level · Group 2

Group 2 — practice question

Separate samples, each of $0.02\ \text{mol}$, of calcium carbonate and barium carbonate are heated until they have fully decomposed into the metal oxide and carbon dioxide.
(a)[2]

State which of these two Group 2 carbonates needs the higher temperature before decomposition begins. Explain your answer.

(b)[3]

Once decomposition is complete, the $0.02\ \text{mol}$ sample of calcium oxide is removed and added to $2.00\ \text{dm}^3$ of water. A solution forms and no solid is present. Dilute sulfuric acid is then added drop by drop until a precipitate is observed. The same steps are then carried out with the $0.02\ \text{mol}$ sample of barium oxide, using the same concentration of dilute sulfuric acid. Identify the sample that needs the larger amount of sulfuric acid for a precipitate to appear. Explain your answer. In your response, refer to the solubilities of the precipitates and the relevant energy terms.

(c(i))[1]

Calculate the mass, in g, of $\text{CO}_2$ obtained from the decomposition of $0.020$ moles of calcium carbonate.

(c(ii))[2]

Calculate the minimum mass, in g, of propane that would produce the same mass of $\text{CO}_2$ as in (c)(i) when it undergoes complete combustion. Give your answer to three significant figures.

Worked solution & mark scheme

This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: $\mathrm{BaCO_3}$ / barium carbonate

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