Question

The correct increasing order of solubility of the sulphates in water is

• A. $ \text{BeS}{{\text{O}}_{\text{4}}}>\text{ MgS}{{\text{O}}_{\text{4}}}>\text{ CaS}{{\text{O}}_{\text{4}}}>\text{ } $ $ \text{SrS}{{\text{O}}_{\text{4}}} $ $ >\text{ BaS}{{\text{O}}_{\text{4}}} $
• B. $ \text{BaS}{{\text{O}}_{\text{4}}}\text{ }>\text{ SrS}{{\text{O}}_{\text{4}}}\text{ }>\text{ CaS}{{\text{O}}_{\text{4}}}\text{ }>\text{ MgS}{{\text{O}}_{\text{4}}} $ $ \text{ }>\text{ BeS}{{\text{O}}_{\text{4}}} $
• C. $ \text{BaS}{{\text{O}}_{\text{4}}}\text{ }>\text{ CaS}{{\text{O}}_{\text{4}}}\text{ }>\text{ SrS}{{\text{O}}_{\text{4}}}\text{ }>\text{ BeS}{{\text{O}}_{\text{4}}} $ $ \text{ }>\text{ MgS}{{\text{O}}_{\text{4}}} $
• D. $ \text{BaS}{{\text{O}}_{\text{4}}}\text{ }>\text{ SrS}{{\text{O}}_{4}}>\text{ MgS}{{O}_{\text{4}}}\text{ }> $ $ \text{CaS}{{\text{O}}_{\text{4}}}\text{ } $ $ ~\text{ }>\text{ BeS}{{\text{O}}_{4}} $

Answer 1

Answer: (A)

The solubility of the sulphates in water decreases down the group
The high solubilities of $ \text{BeS}{{\text{O}}_{\text{4}}} $ and $ \text{MgS}{{\text{O}}_{\text{4}}} $ are due to the high enthalpy of hydration of the smaller $ B{{e}^{2+}} $ and $ M{{g}^{2+}} $ ions, which overcomes the lattice energy factor.