Question

Calculate the concentration of all species in a 0.550 M solution of H2SO3.

[H2SO3], [HSO−3], [SO2−3], [H3O+], [OH−]

Answer 1

H2SO3 is a diprotic acid

H2SO3 + H2O <==> H3O+ + HSO3- ..... Ka1 = [H3O+][HSO3-]/[H2SO3]

let x be the amount dissociated

1.2 x 10^-2 = x^2/0.550 - x

x^2 + 1.2 x 10^-2x - 6.6 x 10^-3 = 0

x = 0.0755 M

[H3O+] = 0.0755 M

[OH-] = 1 x 10^-14/0.0755 = 1.32 x 10^-13 M

[H2SO3] = 0.55 - 0.0755 = 0.4745 M

HSO3- + H2O <==> H3O+ + SO3^2- .... Ka2 = [H3O+][SO3^2-]/[HSO3-]

let x be the amount of dissociation

6.6 x 10^-8 = x^2/0.0755

x = 7.06 x 10^-5 M

[HSO3-] = 0.0755 - 7.06 x 10^-5 = 0.0754 M

[SO3^2-] = 7.06 x 10^-5 M