At `25^(@)C` , the dissociation constants of `CH_(3)COOH` and `NH(4)OH` in aqueous solution are almost same `(10^(-5))`. If pH of same acetic acid solution is 3. The pH solution of `NH_(4)OH` of same conc. At the same temperature would be

Options

A. `3.0`
B. `4.0`
C. `10.0`
D. `11.0`

Answer

D

Explanation

pH of `CH_(3)COOH` sol `=3 `
`:. [H_(3)O^(+)]=sqrt(c xx K_(a))=10^(-3)`
or `10^(-3)=sqrt(c xx 10^(-5))` or `c =10^(-1)M`
`K_(b)=K_(a)=10^(-5)`
pH of `10^(-3)` M solution of `NH_(4)OH`
`[OH^(-)]=sqrt(c xx K_(b))`
`=sqrt(10^(-1) xx 10^(-5))=10^(-3)`
`pOH =3 ` or `pH =14-3=11`