Question

Solubility of the salts of group II A(alkaline earth metals) is in order

• A. $Be ( OH )_{2}< Mg ( OH )_{2}< Ca ( OH )_{2} < Sr ( OH )_{2}< Ba ( OH )_{2}$
• B. $BeCO _{3}< MgSO _{4}< CaSO _{4}< SrSO _{4}< BaSO _{4}$
• C. $BeCO _{3}< MgCO _{3}< CaCO _{3}< SrCO _{3}< BaCO _{3}$
• D. All of the above are correct variations

Answer 1

Answer: (A)

Going down the group, size of the cation increases. Since, the lattice energy decreases much more than the hydration energy with increasing size solubility of hydroxide increases (when size of cation and anion are of comparable size).

(b) and (c) if the anion is large (as $CO _{3}^{2-}, SO _{4}^{2-}$ ) compared to cation, the lattice energy will remain almost constant. Since, hydration energu decreases fown a group, solubility will decrease hence (b) and (c) are incorrect.