A 1.00 L buffer solution is 0.250 mol L^-1 in HF and 0.250 mol L^-1 in LiF. Calculate the pH of the solution after the addition of 0.150 moles of solid LiOH. Assume no volume change upon the addition of the base. The K_a for HF is 3.5 × 10^-4. A) 3.46 B) 4.06 C) 2.85 D) 3.63 E) 4.24

Question

Quizplus · Accepted Answer

The addition of LiOH will convert HF to F⁻, increasing the concentration of F⁻ and decreasing HF. Using the Henderson-Hasselbalch equation, pH = pKa + log([F⁻]/[HF]), where pKa = -log(3.5 × 10⁻⁴) = 3.46. After the reaction, [F⁻] = 0.400 M and [HF] = 0.100 M, so pH = 3.46 + log(0.400/0.100) = 4.06.

A 100 L Buffer Solution Is 0