What is the minimum pH required to prevent the precipitation of ZnS in a solution that is 0.01 M `ZnCl_(2)` and saturated with 0.10 M `H_(2)S` ?
`["Given" :K_(sp)=10^(-21),K_(a_1)xxK_(a_2)=10^(-20)]`

Answer

1

Explanation

`K_(sp)=[Zn^(2+)][S^(-2)]`
:. [5^2]=10^(-21)/10.01=10^(-19)`
`K_(a_1)xxK_(a_2)=([H^+]^(2)[10^(-19)])/0.1implies 10^(-20)=([H^+]^(2)[10^(-19)])/0.1`
`[H^+]=10^(-1)`
pH=1