Question

$CuS{O}_4$ decolourises on addition of KCN, the product is

• A. $\left[Cu\right(CN{)}_4{]}^{2-}$
• B. $C{u}^{2+}$ gets reduced to form $\left[Cu\right(CN{)}_4{]}^{3-}$
• C. $Cu(CN{)}_2$
• D. $CuCN$

Answer 1

The correct option is B $C{u}^{2+}$ gets reduced to form $\left[Cu\right(CN{)}_4{]}^{3-}$

$CuS{O}_4+2KCN\to Cu(CN{)}_2+K_{2}S{O}_4$
$2Cu(CN{)}_2\to 2Cu(CN)+CN$
on stable CN
$CuCN+3KCN\to 3K^{+}\left[Cu\right(CN{)}_4{]}^{3-}$