Answer to Question #202792 in Chemistry for Shaza

Question

A solution of hydrofluoric acid has a molar concentration of 0.01 mol/L, what is the pOH

of the solution? Ka=6.6x 10^-39

Answer 1

According to the equation:

HF + H₂O = H₃O⁺ + F^-

K_a = [H₃O⁺] [F^-] / [HF]

From here:

[H₃O⁺] [F^-] = [HF] × K_a

[H₃O⁺]² = [HF] × K_a = 0.01 mol/L × 6.6 × 10^-4 mol/L = 6.6 × 10^-6

[H₃O⁺] = (6.6 × 10^-6)^1/2 = 8.1 × 10^-3 mol/L

pH = -log[H₃O⁺] = -log(8.1 × 10^-3) = 2.1

pOH = 14 - pH = 14 - 2.1 = 11.9

Answer: 11.9