Question

A weak acid HX has `K_(a) =1 xx 10^(-5)M`. If forms a salt NaX on reaction with alkali. The perentage degree of dissociation of 0.1 M solution of NaX is
A. 1.0E-5
B. 0.01
C. 0.1
D. 0.15

Answer 1

Correct Answer - B
`underset(("Salt"))(X^(-)) +H_(2)O hArr HX+OH^(-)`
For the salt `K_(h) =(K_(w))/(K_(a)) =Calpha^(2)`
`:. (10^(-4))/(10^(-5)) =0.1 alpha^(2)`
`" or "" "alpha^(2) =(10^(-14))/(10^(-6)) =10^(-8)`
`alpha =(10^(-8))^(1//2) =10^(-4)`
`% " degree of dissociation "underset(=10^(-2) =0.01%)(=10^(-4) xx 100)`