Question

All sulphates of alkaline earth metals are not soluble in water. Which is the right order for their solubility?

• A. $Mg>Ca>Ba>Be>Sr$
• B. $Be>Mg>Ca>Sr>Ba$
• C. $Be>Ca>Mg>Ba>Sr$
• D. $Mg>Be>Ba>Ca>Sr$

Answer 1

Answer: (B)

$Be>Mg>Ca>Sr>Ba$
On moving down the group lattice energy remains almost constant as the sulphate is so big that small increase in the size of the cations from Be to Ba does not make any difference. However the hydration energy decreases from $B{e}^{+2}$ to $B{a}^{+2}$ . This causes decrease in the solubility of the sulphates as the ionic size increases.