Weak Base Strong Acid Titrations

Concept #1: Understanding Weak Acid–Strong Base titration reactions

Concept #2: If you use an ICF Chart and at the end you have remaining weak acid and conjugate base then you have a buffer so you use the Henderson-Hasselbalch Equation to find pH. 

Concept #3: If any excess moles of the strong acid remain then we will use its concentration to find the pH of the solution. 

Concept #4: If the moles of both the conjugate base and strong acid are equal then we will have only weak acid at the end of our ICF Chart Calculation. To find pH we would follow up with an ICE Chart. 

Example #1:

A buffer contains 167.2 mL of 0.25 M propanoic acid, CH₃CH₂COOH, with 138.7 mL of 0.42 M sodium propanoate, CH₃CH₂COONa. Find the pH after the addition of 150.2 mL of 0.56 M HCl. The K_a of CH₃CH₂COOH is 1.3 x 10^-5.

Example #2: Calculate the pH of the solution that results from the mixing of 75.0 mL of 0.100 M NaC₂H₃O₂ and 75.0 mL of 0.150 M HC₂H₃O₂ with 0.0025 moles of HBr. K_a of HC₂H₃O₂ is 1.8 x 10^-5.