Question

A) the pH of a 0.150 M solution of a weak monoprotic acid having Ka= 1.2×10⁻³ is 1.89.

Find the percent dissociation of this solution.

B) Find the pH of a 0.150 M solution of a weak monoprotic acid having Ka= 0.13.

Find the percent dissociation of this solution.

Answer 1

A)

The percentage dissociation

B)

Let us represent weak acid as HA

Let x M HA dissociate to reach equilibrium

Initial concentration (M)	0.150	0	0
Change in concentration (M)	-x	+x	+x
Equilibrium concentration (M)	0.150-x	x	x

The acid dissociation constant

This is quadratic equation of type with solution

or

Negative value of x is discarded as concentration cannot be negative.

Hence,

The percentage dissociation