A solution of has and . What is the exact concentration of the sulfide ion, , in the solution? — Ionic Equilibrium Chemistry Question
Question
A solution of $0.1 \text{ M } H_2S$ has $K_{a1} = 10^{-7}$ and $K_{a2} = 10^{-14}$. What is the exact concentration of the sulfide ion, $[S^{2-}]$, in the solution?
Answer: B
💡 Solution & Explanation
In a pure solution of a weak polyprotic acid, the concentration of the divalent anion is strictly equal to its second dissociation constant ($K_{a2}$). Thus, $[S^{2-}] = 10^{-14} \text{ M}$.
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