Final answer:
The Henderson-Hasselbalch equation is used to calculate the pH of a solution that contains both a weak acid and its conjugate base.
Step-by-step explanation:
The Henderson-Hasselbalch equation is used to calculate the pH of a solution that contains both a weak acid and its conjugate base. The equation is pH = pKa + log([A-]/[HA]), where pKa is the negative logarithm of the acid dissociation constant, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the weak acid. To calculate the pH of the given solution, you would need to determine the concentrations of C₂H₅NH₂ and C₂H₅NH₃Br. Then, substitute these values into the Henderson-Hasselbalch equation.