Question

Find the pH and equilibrium concentrations of all species of a 25 M H₂SO₃ solution at 25 degree C.

Answer 1

H2SO3 <----------------------> H+ + HSO3-

25                                          0         0    ---------------> initial

25-x                                       x          x ---------------> equilibrium

Ka1 = [H+][HSO3-]/[H2SO3]

Ka1 = x^2 / 25-x

1.4 x 10^-2 = x^2 / 25-x

x^2 + 1.4 x 10^-2 x - 0.35 = 0

x = 0.585

[H+] = 0.585 M

[HSO3-] = 0.585 M

pH = -log [H+]

pH = 0.233

[H2SO3 ] = 25 -0.585

[H2SO3 ]    = 24.4 M

[SO3-2] = K_a2 = 6.3×10^–8