The pH of basic buffer mixtures is given by : `pH=pK_(a)+log((["Base"])/(["Salt"]))` , whereas pH of acidic buffer mixtures is given by: `pH= pK_(a)+log((["Salt"])/(["Acid"]))`. Addition of little acid or base although shows no appreciable change for all practical purpose, but since the ratio `(["Base"])/(["Salt"])` or `(["Salt"])/(["Acid"])` change, a slight decrease or increase in pH results in.
A solution containing `0.2` mole of dichloroacetic acid `(K_(a)=5xx10^(-2))` and `0.1` mole sodium dichloroacetate in one litre solution has `[H^(+)]` :

Options

A. `0.05M`
B. `0.025M`
C. `0.10M`
D. `0.005M`

Answer

A

Explanation

Since `CHCI_(2). COOH` is relatively strong acid having moer `K_(a)`.
`{:(CHCI_(2).COONararr,CHCI_(2)COO^(-)+,Na^(+)),(,0.1,0.1):}`
`{:(CHCI_(2).COOHhArr,CHCI_(2)COO^(-)+,H^(+)),(0.02,0,0),((0.2-x),(x+0.1),x):}`
`:. K_(a)= ([CHCI_(2)COO^(-)][H^(+)])/([CHCI_(2)COOH])`
or `5xx10^(-2)= ([0.1+x][x])/([0.2-x])` ,
`:. x= 0.05`