For the reaction
`Ag(CN)_(2)^(ɵ)hArr Ag^(o+)+2CN^(ɵ)`, the `K_(c )` at `25^(@)C` is `4 xx10^(-19)` Calculate `[Ag^(o+)]` in solution which was originally `0.1 M` in `KCN` and `0.03 M` in `AgNO_(3)`.

Explanation

`Ag^(+)+2CN hArr Ag(CN)_2`
`K_c=([Ag(CN)_2^-])/([Ag^+][CN]^2)=1/(K_c)=2.5xx10^(20)`
Very high value of `K_c` show that complex forming equilibrium is spontaneous and almost all the `Ag^+` ion would have reacted leaving x M in solution.
`Ag^(+)+2CN hArr [Ag(CN)_2^-]`
Inital 0.03 M 0.1 M 0
At eqm. xM (0.1-0.03xx2) M 0.03 M
`K_c=2.5xx10^(20)=(0.03)/(x(0.1-0.03xx2)^2)`
`therefore x=[Ag^+]=7.5 xx10^(-18)M`