You want to make 2.00 liters of a pH buffer at 7.40 (at 25C) using sodium dihydrogen phosphate (NaH₂PO₄; FW 120.0 g/mol) and disodium hydrogen phosphate (Na₂HPO₄; FW 142.0 g/mol) with a final concentration of total phosphate (NaH₂PO₄ + Na₂HPO₄) equal to 24.0 mM.

a. What are the final concentrations of NaH₂PO₄ and Na₂HPO₄ (individually) needed to satisfy these conditions? Use the appropriate pK value from Table 2-4.

b. What masses of NaH₂PO₄ and Na₂HPO₄ would you use to make this pH buffer? Give your answers to the nearest 0.1 g.