(i) What is buffer solution? Give an example for an acidic buffer and a basic buffer.
(ii) The value of `K_(sp)` of two sparingy soluble salts `Ni(OH)_(2)` and AgCN are `2.0 times 10^(-15) " and "6 times 10^(-17)` respectively. Which salt is more soluble? Explain.

Explanation

(i) 1. Buffer is a solution which consists of a mixture of weak acid and its conjugate base (or) or a weak base and its conjugate acid.
2. This buffer solution resists drastic changes in its pH upon addition of a small quantities of acids (or) bases and this ability is called buffer action.
3. Acidic buffer solution : Solution containing acetic acid and sodium acetate.
Basic buffer solution : Solution containing `NH_(4)O" and " NH_(4)Cl`.
(ii) `AgCN iff Ag^(+)+CN^(-)`
`K_(sp)=[Ag^(+)][CN^(-)]=6 times 10^(-17)`
`Ni(OH)_(2) iff Ni^(2+)+2OH^(-)`
`K_(sp)=[Ni^(2+)][OH^(-)]^(2)=2 times 10^(-15)`
Let `[Ag^(+)]=S_(1), " then "[CN^(-)]=S_(1)`
Let `[Ni^(2+)]=S_(2), " then "[OH^(-)]=2S_(2)`
`S^(2)""_(1)=6 times 10^(-17), S_(1)=7.8 times 10^(-9)`
`(S_(2))(2S_(2))^(2)=10^(-15), S_(2)=0.58 times 10^(-4)`
`Ni(OH)_(2)` is more soluble than AgCN.