Question

The values of `K_(sp)` of two sparingly solubles salts, `Ni(OH)_(2)` and `AgCN` are `2.0 xx 10^(-15)` and `6 xx 10^(-7)` respectively, which salt is more soluble? Explain

Answer 1

`AgCN hArr Ag^(+) + CN^(-)`
`K_(sp) = [Ag^(+)][CN^(-)] = 6 xx 10^(-17)`
`Ni(OH)_(2) hArr Ni^(2+) + 2OH^(-)`
`K_(sp) = [Ni^(2+)][OH^(-)]^(2)=2xx10^(-15)`
Let `[Ag^(+)] = S_(1),` then `[CN] = S_(1)`
Let `[Ni^(2+)] = S_(2)`, then `[OH^(-)] = 2S_(2)`
`S_(1^(2)) = 6 xx 10^(-17), S_(1) = 7.8 xx 10^(-9)`
`(S_(2))(2S_(2))^(2) = 2 xx 10^(-15), S_(2) = 0.58 xx 10^(-4)`
`Ni(OH)_(2)` is more soluble than `AgCN`.