CAIE A-Level Chemistry 27.1.2 Group 2 Solubility and ΔHsol

Practise explaining hydroxide and sulfate solubility trends from changes in lattice and hydration enthalpy.

Exam points

state hydroxide solubility increases while sulfate solubility decreases down Group 2
compare how both formation lattice and hydration enthalpies become less exothermic as ion size increases
identify which enthalpy changes more and use their difference to explain the sign/trend of ΔHsol

[Maximum number: 4]

Describe and explain how the solubility of the Group 2 sulfates varies down the group.

M1 solubility decreases down the group

M2 $\Delta H_{\text {latt }}$ and $\Delta H_{\text {hyd }}$ both become less exothermic / more endothermic

M3 $\Delta H_{\text {latt }}$ changes less (than $\Delta H_{\text {hyd }}$ as $\mathrm{SO}_{4}{ }^{2-}$ being larger than $\mathrm{M}^{2+}$ )

M4 $\Delta H_{\text {sol }}$ becomes less exothermic / less negative

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27.1.2—Trends: the variation in solubility question 1