## Chemistry: The Molecular Science (5th Edition)

The pH of this buffer is equal to $6.77$.
1. Check if the ratio is between 0.1 and 10: - $\frac{[Base]}{[Acid]} = \frac{0.25}{0.1}$ - 2.5: It is. 2. Check if the compounds exceed the $K_a$ by 100 times or more: - $\frac{0.25}{ 4.3 \times 10^{-7}} = 0.5814\times 10^{6}$ - $\frac{0.1}{ 4.3 \times 10^{-7}} = 0.2326\times 10^{6}$ 3. Using the Henderson–Hasselbalch equation: $pH = pKa + log(\frac{[Base]}{[Acid]})$ $pH = 6.37 + log(\frac{0.25}{0.1})$ $pH = 6.37 + 0.3979$ $pH = 6.77$