Question

Which one of the following mixed sulphates is not an alum ?

• A. $K_{2}S{O}_4.A{l}_2(S{O}_4{)}_3.24H_{2}O$
• B. $K_{2}S{O}_4.C{r}_2(S{O}_4{)}_3.24H_{2}O$
• C. $N{a}_{2}S{O}_4.F{e}_2(S{O}_4{)}_3.24H_{2}O$
• D. $CuS{O}_4.A{l}_2(S{O}_4{)}_3.24H_{2}O$

Answer 1

The correct option is D

$CuS{O}_4.A{l}_2(S{O}_4{)}_3.24H_{2}O$

Alums contain monovalent $M^{+}$ and trivalent $M^{+3}$ ions $CuS{O}_4.A{l}_2(S{O}_4{)}_3.24H_{2}O$ has $C{u}^{+2}$ and $A{l}^{+3}$ ions