We’re being asked to calculate the pH of a CH3NH2/CH3NH3Cl buffer solution after the addition of HCl solution. The buffer solution is made up of 0.25 M CH3NH3Cl and 0.25 M CH3NH2
CH3NH3Cl dissociates completely into: CH3NH3+ + Cl-
Since the solution is a buffer, we know that CH3NH3+ is a weak acid and CH3NH2 is the conjugate base. HCl will react with the base CH3NH2
HCl will release hydronium ions (H3O+) ins solution.
Reaction: CH3NH2(aq) + HCl(aq) → NH4+(aq) + Cl-(aq) + H2O(l)
Calculate the pH of a solution prepared by adding 20.0 mL of 0.100 M HCl to 80.0 mL of a buffer that is comprised of 0.25 M CH 3NH 2 and 0.25 M CH 3NH 3Cl. Kb of CH3NH 2 = 6.8 x 10 -5.