An aqueous solution of glycine has pH — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

In aqueous solution, glycine exists predominantly as a zwitterion. Its pH corresponds to its isoelectric point (pI), which is the average of its $pK_a$ and the $pK_a$ of its conjugate acid (derived from $K_b$). The $pK_a$ of the $-\text{N}^\oplus\text{H}_3$ group is 9.8. The $pK_a$ for the $-\text{COOH}$ group is $14 - pK_b = 14 - 11.6 = 2.4$. The pH of the solution is $\frac{9.8 + 2.4}{2} = \frac{12.2}{2} = 6.1$. Therefore, correct answer is C.