Q45 / 180 · AIIMS 2017 · Chemistry

The correct order of solubility of the following compounds in water is

  • A
    $\mathrm{Ba}(\mathrm{OH})_2 < \mathrm{Mg}(\mathrm{OH})_2$
  • B
    $\mathrm{BaCO}_3>\mathrm{CaCO}_3$
  • C
    $\mathrm{Ca}(\mathrm{OH})_2 \simeq \mathrm{Mg}(\mathrm{OH})_2$
  • Correct answer
    D
    $\mathrm{CaSO}_4 < \mathrm{MgSO}_4$

Solution

$\mathrm{MgSO}_4$ is readily soluble in water. With increase in size of the central metal ion, the solubility of the sulphates of alkaline earth metals decreases as the hydration enthalpy from $\mathrm{Be}^{2+}$ to $\mathrm{Ba}^{2+}$ decreases down the group. Therefore, $\mathrm{MgSO}_4$ is more soluble in water than $\mathrm{CaSO}_4$.

Hence, the correct answer is option: 'D'.

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