An acid HA ionises as
`HA hArr H^(+)+A^(-)`
The pH of 1.0 M solution is 5. Its dissociation constant would be :

Options

A. 5
B. `5xx10^(-8)`
C. `1xx10^(-5)`
D. `1xx10^(-10)`

Answer

D

Explanation

`pH=5`
`[H^(+)]=10^(-5) " "[H^(+)]=sqrt(K_(a)C)`
or `K_(a)=([H^(+)]^(2))/(C )=((1xx10^(-5))^(2))/(1.0)=1xx10^(-10)`