The equivalent conductance of `M//32` solution of a weak monobasic acid is `8.0 " mho cm"^(2)` and at infinite dilution is `400 mho cm^(2)`. The dissociation constant of this acid is :

Options

A. `1.25 xx 10^(-6)`
B. `6.25 xx 10^(-4)`
C. `1.25 xx 10^(-4)`
D. `1.25 xx 10^(-5)`

Answer

D

Explanation

`alpha = (Lambda)/(Lambda_(m)) = (8)/(400) = 2 xx 10^(-2)`
Dissociation constant , `K = C alpha^(2)`
`K = (1)/(32) xx (2 xx 10^(-2))^(2) = 1.25 xx 10^(-5)`