In quantitative analysis of second group in laboratory H2S gas is passed in acidic medium for precipitation. When Cu2+ and Cd2+ react with KCN, then for product, true statement is 

(a) K2[Cu(CN)4] more soluble 

(b) K2[Cd(CN)4] less stable 

(c) K3[Cu(CN)2] less stable 

(d) K2[Cd(CN)3] more stable.

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1 Answers

The correct option is : (c) K3[Cu(CN)2] less stable 

Explanation :

K3[Cu(CN)2] = 3(+1) + x + 2(-1) = 0

=> x = -1

As the oxidation no. of 'cu' is -1(-ve), so this complex is unstable and is not formed.

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