posted by MARY .
A buffer, consisting of H2PO4− and HPO42−, helps control the pH of physiological fluids. Many carbonated soft drinks also use this buffer system. What is the pH of a soft drink in which the major buffer ingredients are 7.20 g of NaH2PO4 and 4.90 g of Na2HPO4 per 355 mL of solution?
Use the Henderson-Hasselbalch equation.
pH = pKa + log (base)/(acid)
base = Na2HPO4 converted to mols/L
acid = NaH2PO4 converted to moles/L