What is the pH of an aqueous solution that is 0.60 (CH₃)₃N (K_b = 6.5 * 10^-⁵) and 0.95 M (CH₃)₃NHCl?

Question

Quizplus · Accepted Answer

The solution contains a weak base (CH3NH2) and its salt (CH3NH3Cl), forming a buffer system. The pH of a buffer can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]), where pKa is the negative log of the acid dissociation constant (Ka) of the conjugate acid of the base, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the acid form. Given that the pKa of CH3NH3+ (the conjugate acid of CH3NH2) is 10.65 (since Ka = 6.5 x 10^-11 and pKa = -log(Ka)), and the concentrations of CH3NH3+ (from CH3NH3Cl) and CH3NH2 are 0.95 M and 0.60 M respectively, substituting these values into the Henderson-Hasselbalch equation gives a pH close to 9.61.

What Is the PH of an Aqueous Solution That Is