Question

The dissociation constant of a substitude benzoic acid at `25^(@)C` is `1.0xx10^(-4)`. The pH of a `0.01M` solution of its sodium salt is

Answer 1

Correct Answer - 8
Given, `K_(a)= 1.0xx10^(-4)`
`pK_(a)= -log K_(a)= -log(1.0xx10^(-4))=4`
and `c = 0.01M`
Now, `pH= 7+(1)/(2)(pK_(a)+logc) at 25^(@)C`
`pH= 7+(1)/(2)[4+log(0.01)]`
`=7+1=8`