Question

Alkali metals readily react with oxyacids forming corresponding salts like $M_2{CO}_3$, $MH{CO}_3$, $MN{O}_3$, $M_2{SO}_4$, etc. with evolution of hydrogen. They also dissolve in liquid ${NH}_3$ but without the evolution of hydrogen. The color of its dilute solution is blue but when it is heated and concentrated then its color becomes bronze.

Which of the following statement about the sulphate of alkali metal is correct :

• A. except ${Li}_2{SO}_4$ all sulphate of other alkali metals are soluble in water.
• B. all sulphates of alkali metals except lithium sulphate forms alum.
• C. the sulphates of alkali metals cannot be hydrolysed.
• D. all of these.

Answer 1

The correct option is D all of these.

Except ${Li}_2{SO}_4$ all sulphate of other alkali metals are soluble in water and forms alum. Thus, they form double salts with the sulphates of trivalent metals like $Al,Fe,Cr$ etc. The sulphates of alkali metals cannot be hydrolysed as they are salts of a strong acid and strong base.