AP Chemistry / Unit 8: Acids and Bases
8.9 Henderson-Hasselbalch Equation
Notes
$$pH=pK_a+\log\frac{[A^-]}{[HA]}$$
Practice
$pK_a=4.74$, $[A^-]=[HA]$. pH:
$\log1=0$.
$pK_a=5$, $\displaystyle \frac{[A^-]}{[HA]}=10$. pH:
$5+\log10$.
To make a pH 4 buffer, choose an acid with $pK_a$ near:
pH ≈ $pK_a$.
Ready for more? Take the Unit 8 test.