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. `1.25xx 10^(-4)`
B. `1.25xx10^(-5)`
C. `1.25 xx 10^(-6)`
D. `6.25xx10^(-4)`

Answer

B

Explanation

`alpha=(A_(C))/(A_(oo))=(8)/(400)`
`K_(a)=C alpha^(2)`
`=(1)/(32)xx(8)/(400)xx(8)/(400)`
`=1.25xx10^(-5)`