Chemistry 9701 · AS & A Level · Group 2

Group 2 — practice question

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

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

(b)[3]

Once decomposition is complete, the $0.02\ \text{mol}$ sample of calcium oxide is placed in $2.00\ \text{dm}^3$ 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 procedure is then carried out with the $0.02\ \text{mol}$ sample of barium oxide, using dilute sulfuric acid of the same concentration. Identify the sample for which the greater amount of sulfuric acid must be added for a precipitate to appear. Explain your answer. You should refer to the solubilities of the precipitates and the relevant energy terms in your answer.

(c(i))[1]

Calculate the mass, in g, of $\text{CO}_2$ made when $0.020$ moles of calcium carbonate decompose.

(c(ii))[2]

Calculate the minimum mass, in g, of propane that would, when completely combusted, produce the same mass of $\text{CO}_2$ found in (c)(i). 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: It is barium carbonate / $\mathrm{BaCO_3}$

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