question_answer

In the separation of \[C{{u}^{2+}}\] and \[C{{d}^{2+}}\] in 2nd group of qualitative analysis of cations, tetramine copper (II) sulphate and tetrammine cadmium (II) sulphate react with KCN to form the corresponding cyano complexes, which one of the following pairs of the complexes and their relative stability enables the separation of \[C{{u}^{2+}}\] and \[C{{d}^{2+}}\]?                               [AIPMT 2000]

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