Question

Calculate the solubility of `AgCN` in a buffer solution of `pH = 3`, Given `K_(sp) of AgCN = 1.2 xx 10^(-16)` and `K_(a)` for `HCN = 4.8 xx 10^(-10)`.

Answer 1

Solubility of salt of weak acid `(AgCN)` in a buffer is given by the formula:
`S` in buffer `=[K_(sp)(1+(H^(o+))/(K_(a)))]^((1)/(2))`
`=[1.2 xx 10^(-16) (1+(10^(-3))/(4.8xx10^(-10)))]^((1)/(2))`
`= [1.2 xx 10^(-16) (1+2.08 xx 10^(6))]^((1)/(2))`
`=[1.2 xx 10^(-16) (~~2.08 xx 10^(6))]^((1)/(2))`
`= sqrt(2.496) xx 10^(-5) = 1.5 xx 10^(-5)M`