The number of `S^(2-)` ions present in `1L` of `0.1 MH_(2)S [K_(a(H_(2)S)) = 10^(-21)]` solution having `[H^(o+)] = 0.1M` is:

Options

A. `6.023 xx 10^(3)`
B. `6.023 xx 10^(4)`
C. `6.023 xx 10^(5)`
D. `6.023 xx 10^(6)`

Answer

A

Explanation

`H_(2)S hArr 2H^(o+) +S^(2-)`
`:. K_(a) = ([H^(o+)]^(2)[S^(2-)])/([H_(2)S])`
`10^(-21) = (0.1 xx 0.1 xx[S^(2-)])/(0.1)`
`:. [S^(2-)] = 10^(-20) M = 10^(-20) xx 6.023 xx 10^(23)`
`= 6.023 xx 10^(3) ions`