question_answer

Solubility of the alkaline earth's metal sulphates in water decreases in the sequence [NEET 2015 (C)]

A) \[Mg>Ca>Sr>Ba\]        

B) \[Ca>Sr>Ba>Mg\]

C) \[Sr>Ca>Mg>Ba\]        

D) \[Ba>Mg>Sr>Ca\]

Correct Answer: A

Solution :

[a] Solubility of the sulphates. The sulphates becomes less soluble as you go down the group i.e.                       Mg > Ca > Sr > Ba The magnitude of the lattice energy remains almost constant as the size of the sulphate ion is so big that small increase in the size of the cation from Be to Ba does not make any difference. However, the hydration energy decreases from  to  appreciably as the size of the cation increases down the group. The significantly high solubility of  is due to high enthalpy of solvation of the smaller  ions.