Chemistry · EQUILIBRIUM

For a 0.10 M aqueous solution of a diprotic acid \( \text{H}_2\text{X} \), the ionization constants are \( K_{a_1} = 4.0 \times 10^{-5} \) and \( K_{a_2} = 1.6 \times 10^{-11} \). The concentration of divalent anion \( [\text{X}^{2-}] \) at equilibrium is:

1. A
   \( 4.0 \times 10^{-6}\text{ M} \)
2. B
   \( 2.0 \times 10^{-3}\text{ M} \)
3. C
   \( 3.2 \times 10^{-13}\text{ M} \)
4. D
   \( 1.6 \times 10^{-11}\text{ M} \)