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

$CH_3COOH$ and $NaCH_3COO$ are not the best combination for a buffer with $pH \approx 9$, because the $pKa$ for acetic acid is not close to 9.
1. Identify the acid: $CH_3COOH$. 2. Calculate its pKa: $pKa = -log(Ka)$ $pKa = -log( 1.8 \times 10^{- 5})$ $pKa = 4.75$ 3. Compare this number to 9. - It is not approximately 9, therefore, these compounds are not the best combination for a buffer with a pH $\approx$ 9.