A buffer solution is made by making a 100 mL aqueous solution containing 2.6 grams of citric acid (C6H8O7) and 6.4 grams of potassium citrate (C6H7O7K). What is the pH of this buffer solution? Citric acid is a triprotic acid with pKa1 = 4.77, pKa2 = 4.77, and pKa3 = 5.19.