Which of the following are buffer solutions? Give reason.
100 mL 0.1 `(M)CH_(3)COONa+25mL0.1(M)HCl`

Explanation

100 mL of 0.1(M) `CH_(3)COONa-=0.01` mol of `CH_(3)COONa and 25 mL` of 0.1(M) `HCl-=0.0025mol` of HCl.
In the mixed solution, 0.0025 mol of HCl reacts completely with the same amount of `CH_(3)COONa`, forming `CH_(3)COONa` remains in the solution is `(0.01-0.0025)=7.5xx10^(-3)` mol. therefore, the mixed solution contains `CH_(3)COOH` and its salt `CH_(3)COONa`. hence, it is a buffer solution.