Limewater is water containing a saturated solution of $\text{Ca(OH)}_2$. It is used as a test for the presence of $\text{CO}_2$ in a gas mixture.
(a(i))[1]
Write an equation showing the reaction of limewater with $\text{CO}_2$.
(a(ii))[1]
Explain why a saturated solution of $\text{Ba(OH)}_2$ is suitable for testing for $\text{CO}_2$.
(a(iii))[2]
Explain why a saturated solution of $\text{Mg(OH)}_2$ is unsuitable for testing for $\text{CO}_2$.
(b)[3]
Describe and explain how the thermal stabilities of the carbonates change down Group 2.
(c)[2]
Nickel carbonate, $\text{NiCO}_3$, decomposes when heated. Use the Data Booklet to explain whether $\text{NiCO}_3$ will decompose more readily or less readily than $\text{CaCO}_3$.
Worked solution & mark scheme
This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: “The correct equation is: calcium hydroxide reacts with carbon dioxide to make calcium carbonate and water: $\text{Ca(OH)}_2 + \text{CO}_2 \rightarrow \text{CaCO}_3 + \text{H}_2\text{O}$” …