Ncert Exercises & Solutions

Which of the following complexes formed by Cu⁺⁺ ions is most stable?

Hint: Stability of complex directly proportional to the logK value

The greater the value of logK, the greater will be the stability of complex compounds formed

For reaction,

${Cu}^{2} + 4 {CN}^{-} \to {[Cu {(CN)}_{4}]}^{2 -}$
$K = \frac{{[Cu {(CN)}_{4}]}^{2 -}}{[{Cu}^{2 +}] {[{CN}^{-}]}^{4}} and logK = 27.3$

For this reaction, log K has the highest value among the given four reactions. Hence, K will

also be higher. Hence, it will have a higher stability.