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

$Na_2HPO_4$ and $Na_3P{O_4}$ are not the best combination for a buffer solution with pH $\approx$ 7.
1. Identify the acid: $HP{O_4}^{2-}$. 2. Calculate its pKa: $pKa = -log(Ka)$ $pKa = -log( 4.6 \times 10^{- 13})$ $pKa = 12.34$ 3. Compare this number to 7. - It is not approximately 7, therefore, these compounds are not the best combination for a buffer with neutral pH.