Describe and explain how the solubilities of the hydroxides of the Group 2 elements change.
Reaction 1 happens when $\text{CO}_2(g)$ is passed through an aqueous solution of $\text{Ba(OH)}_2$. Use the table data to find the standard enthalpy change for reaction 1, $\Delta H^{\ominus}_{r1}$. The reaction is: $\text{Ba(OH)}_2(aq) + \text{CO}_2(g) \rightarrow \text{BaCO}_3(s) + \text{H}_2\text{O}(l)$.
If $\text{CO}_2(g)$ is bubbled through an aqueous solution of $\text{Ba(OH)}_2$ for long enough, the $\text{BaCO}_3(s)$ precipitate dissolves, as shown in reaction 2. Use this information together with the table data to find the standard enthalpy change of formation of the $\text{HCO}_3^{-}(aq)$ ion. Reaction 2 is: $\text{BaCO}_3(s) + \text{CO}_2(g) + \text{H}_2\text{O}(l) \rightarrow \text{Ba(HCO}_3)_2(aq)$. $\Delta H^{\ominus}_{r2} = -26\ \text{kJ mol}^{-1}$.
Reaction 3 shows the overall change. Use your answer to (ii) together with the table data to calculate the standard enthalpy change for reaction 3, $\Delta H^{\ominus}_{r3}$. The reaction is: $\text{Ba(OH)}_2(aq) + 2\text{CO}_2(g) \rightarrow \text{Ba(HCO}_3)_2(aq)$.
How would the value of $\Delta H^{\ominus}_{r3}$ compare with $\Delta H^{\ominus}_{r4}$ for the similar reaction using $\text{Ca(OH)}_2(aq)$, as shown in reaction 4? Explain your answer. Reaction 4 is: $\text{Ca(OH)}_2(aq) + 2\text{CO}_2(g) \rightarrow \text{Ca(HCO}_3)_2(aq)$.
The standard entropy change for reaction 1 is $\Delta S^{\ominus}_{r1}$. Suggest, with a reason, how the standard entropy change for reaction 3 may compare with $\Delta S^{\ominus}_{r1}$.