A buffer solution is composed of 1.271 g of KH2PO4 and 4.633 g of Na2HPO4 . (Ka for dihydrogen phosphate ion is 6.2x10^-8).
a. What is the pH of the buffer solution?
b. What mass of KH2PO4 must be added to decrease the buffer solution pH by 0.10 unit from the value calculated in part a?