Which of the following complex formed by `Cu^(2+)` ions is most stable?

Options

A. `Cu^(2+) + 4NH_(3) rarr [Cu(NH_(3))_(4)]^(2+), log K = 11.6`
B. `Cu^(2+) + 4CN^(-) rarr [Cu(CN)_(4)]^(2-), log K = 27.3`
C. `Cu^(2+) + 2 e n rarr [Cu(e n)_(2)]^(2+), log K = 15.4`
D. `Cu^(2+) + 4H_(2)O rarr [Cu(H_(2)O)_(4)]^(2 +), log K = 8.9`

Answer

D

Explanation

The greater the value of log K, the greater will be stability of complex compound formed.
For reaction, log K has the highest value.
`Cu^(2+) + 4 Cn^(0) rarr [Cu(CN)_(4)]^(2+)`
`K = ([Cu(CN)_(4)]^(2+))/([Cu^(2+)][CN^(-)]^(4))` and log K = 27.3