Answer
PH = 7.15
Work Step by Step
Final volume = 200 mL
Hence, Final molarity of K2HPO4 = 50 mL x 2M / 200 mL = 0.50 M Final molarity of KH2PO4 = 25 mL x 2 M/ 200 mL = 0.25 M pH of the solution is calculated by Henderson equation as,
PH = pka + log [ K2HPO4] / [KH2PO4]
Since, pKa of KHPO4 = 6.85 [K2HPO4] = 0.50 M [KH2PO4] = 0.25 M Hence,
PH = 6.85 + log [0.50 / 0.25] PH = 6.85 + log 2 PH
= 6.85 +0.3010 = 7.151
PH = 7.15
