The amino acid glycine (H₂N–CH₂–COOH) can participate in the following equilibria in water:
H₂N–CH₂–COOH + H₂O ⇌ H₂N–CH₂–COO^– + H₃O⁺ K_a = 4.3 × 10^-3
H₂N–CH₂–COOH + H₂O⇌ ⁺H₃N–CH₂–COOH + OH^- K_b = 6.0 × 10^-5
(b) What is the pH of a 0.050 M aqueous solution of glycine?

Acid-base equilibria involve the transfer of protons (H+) between species in solution. In the case of glycine, it can act as both an acid and a base, participating in equilibria that define its behavior in water. Understanding the dissociation constants (Ka and Kb) is crucial for predicting the pH of the solution, as they indicate the strength of the acid and base forms of glycine.

Dissociation constants, Ka and Kb, quantify the extent to which an acid or base dissociates in water. Ka represents the equilibrium constant for the dissociation of an acid, while Kb represents the equilibrium constant for the dissociation of a base. For glycine, the given values of Ka and Kb allow us to calculate the concentrations of the various species in solution, which is essential for determining the pH.

pH is a measure of the hydrogen ion concentration in a solution, calculated using the formula pH = -log[H+]. In the context of glycine, the pH can be determined by considering the contributions of both the acidic and basic forms of the amino acid in solution. By applying the Henderson-Hasselbalch equation or directly using the dissociation constants, one can find the pH of the glycine solution.