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Chemistry · EQUILIBRIUM
हिन्दीFor 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:
Correct answer · Option 4
\( 1.6 \times 10^{-11}\text{ M} \)
Explanation
In a solution of weak polyprotic acid where \( K_{a_1} \gg K_{a_2} \), \( [\text{H}^+] \approx [\text{HX}^-] \). Substituting into \( K_{a_2} = \frac{[\text{H}^+][\text{X}^{2-}]}{[\text{HX}^-]} \) yields \( [\text{X}^{2-}] \approx K_{a_2} = 1.6 \times 10^{-11}\text{ M} \).
