Question

When aqueous solution of potassium fluoride is added to the blue coloured aqueous $CuS{O}_4$ solution, a green precipitate is formed. This observation can be explained as follows :

• A. on adding $KF$, $H_{2}O$ being weak field ligand is replaced by $F^{-}$ ions forming $[Cu{F}_4{]}^{2-}$ which is green in colour.
• B. potassium is coordinated to $\left[Cu\right(H_{2}O{)}_4{]}^{2+}$ ion present in $CuS{O}_4$ and gives green colour.
• C. on adding $KF$, $C{u}^{2+}$ are replaced by $K^{+}$ forming a green complex.
• D. blur colour of $CuS{O}_4$ and yellow colour of KI form green colour on mixing.

Answer 1

The correct option is A on adding $KF$, $H_{2}O$ being weak field ligand is replaced by $F^{-}$ ions forming $[Cu{F}_4{]}^{2-}$ which is green in colour.

On adding $KF$, $H_{2}O$ being weak field ligand is replaced by $F^{-}$ ions forming $[Cu{F}_4{]}^{2-}$ which is green in colour.

$CuS{O}_4\cdot 5H_{2}O+4KF\to 4K^{+}+[Cu{F}_4{]}^{2-}+S{O}_4^{2-}+5H_{2}O$