Hydrosulfuric acid H2SO3 is a diprotic acid with ionization

Hydrosulfuric acid (H₂SO₃) is a diprotic acid with ionization constants of K_a1 = 5.7 x 10^-8 and K_a2 = 1.0 x 10^-19. Determine the concentration of sulfide ions (SO₃^-2) in a 0.10 M hydrosulfuric solution.

In M? Thank you!!!

Solution

H2SO3 --> H+ + HSO3-

0.1-x..........x.........x

ka1 = 5.7*10^-8 = x^2/(0.1-x)

x = 7.55*10^-5M

HSO3- --> H+ + SO3 2-

x-y.............y........y

ka2 = Y^2/(x-y) = 1*10^-19

y = 2.75*10^-12

[SO3 2-] = 2.75*10^-12 M