A 100.0 mL sample of 0.20 M HF is titrated with 0.10 M KOH.Determine the pH of the solution after the addition of 300.0 mL of KOH.The K_a of HF is 3.5 × 10^-4. A) 12.40 B) 9.33 C) 7.00 D) 8.94 E) 12.00

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Quizplus · Accepted Answer

After adding 300.0 mL of 0.10 M KOH to 100.0 mL of 0.20 M HF, the solution is in excess of KOH, making it basic. The moles of KOH added (0.030 mol) exceed the moles of HF initially present (0.020 mol), leaving 0.010 mol of KOH in excess. The total volume is 400.0 mL, so the concentration of OH⁻ is 0.010 mol / 0.400 L = 0.025 M. The pOH is -log(0.025) = 1.60, and the pH is 14 - 1.60 = 12.40.

A 1000 ML Sample of 0