question_answer

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) \[\text{BaS}{{\text{O}}_{\text{4}}}\text{ }>\text{ SrS}{{\text{O}}_{4}}>\text{ MgS}{{O}_{\text{4}}}\text{ }>\] \[\text{CaS}{{\text{O}}_{\text{4}}}\text{ }\] \[~\text{ }>\text{ BeS}{{\text{O}}_{4}}\]

Correct Answer: A

Solution :

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.