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)`.

Options

A. `7.5xx10^(18)`
B. `7.5xx10^(-18)`
C. `7.5xx10^(19)`
D. `7.5xx10^(-19)`

Explanation

`underset((0.1-0.06))underset(0.1)(2KCN)+underset(0)underset(0.03)(AgNO_(3))hArrunderset((0.03))underset(0)(Ag(CN)_(2)^(-))+underset((0.03))underset(0)(KNO_(3))+underset((0.03))underset(0)(K^(+))`
`:. [Ag(CN)_(2)^(-)]=0.03`
Now, `underset((0.03-a))underset(0.03)(Ag(CN)_(2)^(-))hArrunderset(a)underset(0)(Ag^(+))+underset((0.04+a))underset(0.04"(left from KCN)")(2CN^(-))`
(`:' K_(c)` is small `:. 0.03-a~~0.03` and `0.04+a~~0.04`)
`:. K_(c)=4xx10^(-19)=((0.04)^(2)xxa)/(0.03)`
`a=7.5xx10^(-18)`