Reaction 1: $\text{BaCl}_2\cdot 2\text{H}_2\text{O}(s) + 2\text{SOCl}_2(l) \rightarrow \text{BaCl}_2(s) + 2\text{SO}_2(g) + 4\text{HCl}(g)$. Describe one observation when reaction 1 is carried out.
Define entropy, $S$.
The entropy change, $\Delta S^{\circ}$, for reaction 1 at $25^{\circ}\text{C}$ is $+768\,\text{J K}^{-1}\text{ mol}^{-1}$. Explain why $\Delta S^{\circ}$ has a large positive value.
Table 2.1 gives the enthalpy changes of formation, $\Delta H_f^{\circ}$, for the compounds in reaction 1. Calculate the standard Gibbs free energy change, $\Delta G^{\circ}$, in $\text{kJ mol}^{-1}$, for reaction 1 at $25^{\circ}\text{C}$.
When aqueous solutions of $\text{BaCl}_2$ and $\text{Na}_2\text{Cr}_2\text{O}_7$ are mixed, a yellow precipitate of $\text{BaCrO}_4(s)$ forms and the solution left behind is acidic. Write the ionic equation for this reaction.
Explain why $\text{BaCrO}_4(s)$ is coloured.
Barium sulfate is the least soluble of the Group 2 sulfates. Explain the trend in the solubilities of the Group 2 sulfates.