17.1 Buffers
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Buffer
A buffer is a solution that resists changes in pH.
It is composed of a weak acid and its conjugate base or a weak base and its conjugate acid.
Buffer Range = pKa ± 1
| Acid | pKa |
|---|---|
| HF | 3.2 |
| CH3COOH | 4.8 |
| H2CO3 | 6.4, 10.3 |
| H3PO4 | 2.1, 7.2, 12.4 |
| 3 Ways to Prepare a Buffer |
|---|
| Weak Acid / Conjugate Base1 : 1 |
| Weak Acid / Strong Base2 : 1 |
| Weak Base / Strong Acid2 : 1 |
Calculations with buffers
(Henderson−Hasselbalch Equation)
What is the pH of a solution having 0.10M CH3COOH and 0.080M CH3COONa? (Ka = 1.76×10-5)
What would be the pH if 5.0mL of 0.10M HCl were added to 100mL of the buffer solution above?