Question

A certain weak acid, HA, has a Ka value of 3.2×10−7.

1. Calculate the percent ionization of HA in a 0.10 M solution.

2. Calculate the percent ionization of HA in a 0.010 M solution.

Answer 1

Given that  Ka value = 3.2×10⁻⁷

We know that Ka = ca²   a =  percent ionization

a = (Ka/C)^1/2

a) Given that C = 0.1 M

percent ionization

a = (Ka/C)^1/2

= ( 3.2×10⁻⁷/0.1)^1/2

   = 1.78 x 10^-3

= 0.178 %

Therefore,

percent ionization of HA in a 0.10 M solution = 0.178 %

b)

Given that C = 0.01 M

percent ionization

a = (Ka/C)^1/2

= ( 3.2×10⁻⁷/0.01)^1/2

   = 5.65 x 10^-3

= 0.565 %

Therefore,

percent ionization of HA in a 0.010 M solution = 0.565 %