Question

Calculate the percent ionization of arsenous acid (H₃AsO₃) in solutions of each of the following concentrations (K_a = 5.1e-10.)

(a) 0.206 M

%



(b) 0.556 M

%



(c) 0.822 M

%

Answer 1

The relation between percent ionization a , Ka and C is Ka = Ca²

Then ,

   a = (Ka/C)^1/2

Given that Ka of H₃AsO₃ = 5.1 x 10^-10

a)    C = 0.206 M

      a = (Ka/C)^1/2

             = (5.1 x 10^-10/0.206)^1/2

         = 0.000049

        = 0.0049 %

Therefore,

percent ionization = 0.0049 %

b)    C = 0.556 M

      a = (Ka/C)^1/2

             = (5.1 x 10^-10/0.556)^1/2

         = 0.00003

        = 0.003 %

Therefore,

percent ionization = 0.003 %

c)    C = 0.822 M

      a = (Ka/C)^1/2

             = (5.1 x 10^-10/0.822)^1/2

         = 0.000025

        = 0.0025 %

Therefore,

percent ionization = 0.0025 %