Question

Calculate the concentration of H2SO4, HSO4-, SO4-2 and H+ ions in a 0.17 M sulfuric acid solution. Assume H+ and H3O+ to be the same ions. Ka2 = 1.3 x 10^-2.

Answer 1

Since  H₂SO₄ is a strong acid. So, it will dissociate completely as per the following equation

H₂SO₄   H⁺ + HSO₄^-

Now, as we have 0.17M H₂SO₄ is here,  [H⁺] and   [HSO₄^-] will both be equal to 0.17M.

But HSO₄^- is a weak acid and it dissociate as per the following reaction:

HSO₄^-   H⁺ + SO₄^2- having K_a = 1.3 x 10^-2

Final Concentration 0.17-x x x

So, we have   K_a = x²/ (0.17-x)

  1.3 x 10^-2 = x²/ (0.17-x)

So, x² + 0.013x - 0.00221 = 0

Solving this quadratic equation for x, we get x = 0.0409

So, we have [SO₄^2-] = 0.0409M

[HSO₄^-] = 0.17 - 0.0409 = 0.129M

[H₂SO₄] = 0 as it is a strog acid, fully dissociated.

[H⁺] = 0.17 + 0.0409 = 0.2109M