Question

State whether the given statement is true or false:

Out of $\left[Cu\right(CN{)}_4{]}^{3-}$ and $\left[Cd\right(CN{)}_4{]}^{2-}$, $\left[Cu\right(CN{)}_4{]}^{3-}$ is unstable and gives black precipitate of $CuS$ on passing $H_{2}S$ gas.

• A. True
• B. False

Answer 1

The correct option is B False

The given statement is False.
Out of $\left[Cu\right(CN{)}_4{]}^{2-}$ and $\left[Cd\right(CN{)}_4{]}^{2-}$, $\left[Cd\right(CN{)}_4{]}^{2-}$ is unstable and gives yellow precipitate of $CdS$ on passing $H_{2}S$ gas.
The second ionisation of potassium cadmicyanide is higher than that of potassium cuprocyanide, sufficient $C{d}^{2+}$ ions are present in solution and hence, only $CdS$ is precipitated on passing $H_{2}S$ gas.