A buffer solution contains 0.219 M CH3NH3Cl and 0.428 M CH3NH2 (methylamine). Determine the pH change when 0.097 mol HI is added to 1.00 L of the buffer.
pH after addition - pH before addition = pH change = -0.27
Feedback:
Step 1. Write the balanced equation for the acid hydrolysis reaction.
CH3NH3+(aq) + H2O H3O+ + CH3NH2(aq)
Ka = Kw / Kb(CH3NH2) = 1.0e-14 / 4.2E-4 = 2.4E-11