Chemistry question about pka

Question

As a technician in a large pharmaceutical research firm, you need to produce 300. mL of 1.00 M potassium phosphate solution of pH = 7.44. The pKa of H_2PO_4^- is 7.21. You have 2.00 mL of 1.00M KH_2PO_4 solution and 1.50 mL of 1.00 M K_2HPO_4 solution, as well as a carboy of pure distilled H_2O. How much 1.00M KH_2PO_4 will you need to make this solution?

Answer 1

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