Doubly Sour

Chemistry Level 3

A diprotic acid $\text{H}_2\text{X}$ has $K_1 = 2.0\cdot 10^{-6}$ and $K_2 = 5.0\cdot 10^{-8}$ .

If this acid is present in a solution of $\text{pH } = 7$ , determine the ratio $\dfrac{[\text{X}^{2-}]}{[\text{H}_2\text{X}]}.$