Table 1 shows some enthalpy change data for barium chloride and its constituent ions.
| Process | Enthalpy change / kJ mol−1\text{kJ mol}^{-1}kJ mol−1 |
|---|---|
| Ba2+(g)→Ba2+(aq)\text{Ba}^{2+}\text{(g)} \rightarrow \text{Ba}^{2+}\text{(aq)}Ba2+(g)→Ba2+(aq) | −1305-1305−1305 |
| Cl−(g)→Cl−(aq)\text{Cl}^{-}\text{(g)} \rightarrow \text{Cl}^{-}\text{(aq)}Cl−(g)→Cl−(aq) | −363-363−363 |
| Ba2+(g)+2Cl−(g)→BaCl2(s)\text{Ba}^{2+}\text{(g)} + 2\text{Cl}^{-}\text{(g)} \rightarrow \text{BaCl}_2\text{(s)}Ba2+(g)+2Cl−(g)→BaCl2(s) | −2056-2056−2056 |
Use the data in Table 1 to calculate the molar enthalpy change of solution (ΔHsol\Delta H_{\text{sol}}ΔHsol) when anhydrous barium chloride dissolves in water.
Use your answer to part (a) to deduce how the temperature of the mixture changes when anhydrous barium chloride dissolves in water.
Explain why the enthalpy of hydration of calcium ions, Ca2+\text{Ca}^{2+}Ca2+, is more negative than the enthalpy of hydration of barium ions, Ba2+\text{Ba}^{2+}Ba2+.
27 exam-style questions on AQA A Level Chemistry Thermodynamics (A-level only), covering Born–Haber cycles (A-level only) and Gibbs free-energy change, $\Delta G$ , and entropy change, $\Delta S$ (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.