Buffer soution'A' of a weak monoprotic acid and it's sodium salt in concentreaiton ration X:Y has `pH=(pH)_(1)` and buffer solution 'B' of the same acid and it's sodium salt in the concentration ratio Y:X has `pH=(pH)_(2). If (pH)_(2)-(pH)_(1)+ (pH)_(2)=9.5` units, then:

Options

A. `pK_a=4.75`
B. `x/y=2.36`
C. `x/y=3.162`
D. `pK_a=5.25`

Answer

A,C

Explanation

`(pH)_1=pK_a+log(y//x)`
`(pH)_2=pK_a+log(x//y)`
`(pH)_2-(pH)_1=log(x/y)-log(y/x)=1 implies log(x^2/y^2)=1`
so `x^2/y^2=10 implies x/y=3.162`
`(pH)_2+(pH)_1=2pK_a+log(y/x)+log(x/y)`
`=2 pK_a=9.5`
so, `pK_a=9.5/2=4.75`