Two separate solutions of weak monoprotic acids, () and (), are found to be perfectly isohydric. If — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

Isohydric solutions are solutions of electrolytes that have the exact same concentration of a common ion (in this case, $[H^+]$). For weak acids, $[H^+] \approx \sqrt{K_a \cdot C}$. Equating the two yields $\sqrt{K_{a1}C_1} = \sqrt{K_{a2}C_2}$, which squares to the identity $K_{a1}C_1 = K_{a2}C_2$. Substituting the provided values gives $(10^{-4})(0.1) = (10^{-5}) \cdot C_2 \implies 10^{-5} = 10^{-5} \cdot C_2 \implies C_2 = 1.0 \text{ M}$.