Lactic acid (HC3H5O3, M = 90.1 g/mol) is a weak monoprotic acid, with Ka = 1.4 x 10-4 at T = 25.0 °C. Potassium lactate (KC3H5O3, M = 128.2 g/mol) is the potassium salt of the conjugate base of lactic acid.
A solution is prepared by dissolving 18.46 g of lactic acid in water. The volume of the solution is 1.000 L. How many grams of potassium lactate must be added to the solution to convert it into a pH = 3.60 buffer solution?