In the separation of `Cu^(2+)` and `Cd^(2+)` of Iind group in qualitative analysis of cations, tetraamminecopper (II) sulphate and tetramminecadmium (II) sulphate react with KCN to form the corresponding cyano complex. Which one of the following pairs of the complexes and their relative stability enables the separation of `Cu^(2+)` and `Cd^(2+)` ?

Options

A. `K_(3)[Cu(CN)_(4)]` : less stable and `K_(2)[Cd(CN)_(4)]` : more stable
B. `K_(3)[Cu(CN)_(4)]` : more stable and `K_(2)[Cd(CN)_(4)]` : less stable
C. `K_(2)[Cu(CN)_(4)]` : less stable and `K_(2)[Cd(CN)_(4)]` : more stable
D. `K_(2)[Cu(CN)_(4)]` : more stable and `K_(2)[Cd(CN)_(4)]` : less stable.

Answer

B

Explanation

`K_(3)[Cu(CN)_(4)]` is more stable than `K_(2)[Cd(CN)_(4))]` because `Cu^(+)` is smaller than `Cd^(2+)` and possesses high charge density.