The equivalent conductance of `M//32` solution of a weak monobasic acid is `8.0 ` and at infinite dilution is `400 `. The dissociation constant of this acid is :

Options

A. `1.25xx10^(-5)`
B. `1.25xx10^(-6)`
C. `6.25xx10^(-4)`
D. `1.25xx10^(-4)`

Answer

A

Explanation

`alpha=(^^)/(wedge_(D))=(8.0)/(400)=2xx10^(-2)`
`K_(a)=(Calpha^(2))/((1-alpha))~~Calpha^(2)=(1)/(32)xx(2xx10^(-2))=1.25xx10^(-5)`.