Question

The formula of alum is

• A. $K_{2}SO_{4} Al_{2}(SO_{4})_{3} \cdot 24H_{2}O$
• B. $K_{4}[Fe(CN)_{6}]$
• C. $K_{2}SO_{4} Al_{2}(SO_{4})_{3}\cdot 6H_{2}O$
• D. $Na_{2}CO_{3} \cdot 10H_{2}O$

Answer 1

Answer: (A)

General formula for alum is
$M_{2}SO_{4}.R_{2}(SO_{4})_{3}.24H_{2}O$
$M=$ monovalent cation $(K^{+}, Na^{+}...)$
$R =$ Trivalent cation $(Al^{+3}, Fe^{+3})$
Hence, $K_{2} SO_{4} Al_{2} (SO_{4})_{3} . 24H_{2}O$ represent an alum.