Problem- What is the pH of a buffer that results when 12.0 g of HaH2PO4 and 8.00 g of Na2HPO4 are dilluted with water to a volume of .50L? (Ka of H2PO4^- = 6.2*10^-8, the molar masses of NaH2PO4 and Na2HPO4 are 120.0 g/mol and 142.0 g/mol, respectively).
It is not a question in the book, so I just need the full solution of deriving