Question

Each group will have a stock solution of 1M acetic acid and 1M sodium acetate.
2. Prepare 22mL buffer solution with 0.35M acetic acid and 0.35M sodium acetate. Given
that the Ka of acetic acid is 1.8 x 10-5. What is the expected pH of the buffer? 3. Pipette the prepared buffer solution into two clean containers, each with 10mL buffer
solution. Calculate and measure how the pH change if
a. 2mL 0.025M NaOH is added to tube 1. b. 2mL 0.04M HCl is added to tube 2.
4. Add another volume of solution to each of the buffer solution and check the change of
pH using pH paper and pH meter.
a. 2mL 0.025M NaOH is added to tube 1. b. 2mL 0.04M HCl is added to tube 2.
5. Can the buffer solution resist change of pH after adding acid / base? Explain your
answer.
Exercise b:
- Here are some Ka values for weak acids and bases. Which of the pair(s) would be
appropriate as a buffer at pH = 7.0? Explain your answer.
o CH3COOH/CH3COO- Ka = 1.8 x 10-5
o HCO3-/CO32-
Ka = 5.6 x 10-11 o H2PO4-/HPO42-
Ka = 6.2 x 10-8

Answer 1