Answer
$H_3PO_4$ and $NaH_2PO_4$ are not the best combination.
Work Step by Step
1. Identify the acid:
$H_3PO_4$.
2. Calculate its pKa:
$pKa = -log(Ka)$
$pKa = -log( 7.2 \times 10^{- 3})$
$pKa = 2.14$
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.
