An aqueous solution is prepared by dissolving hydrofluoric acid (HF) to give an…
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
An aqueous solution is prepared by dissolving hydrofluoric acid (HF) to give an initial concentration of 0.250M at 25∘C. The acid-dissociation constant of HF at this temperature is 6.8×10−4.
(a) Calculate [H3O+] and the pH of the solution assuming that the equilibrium concentration of HF is effectively equal to 0.250M.
(b) Solve exactly for [H3O+] by treating the equilibrium concentrations algebraically and obtain the pH without making the assumption stated in part (a).
(c) Determine the percent error in [H3O+] that results from the assumption in part (a).
(d) Based on the percent error, state whether the assumption is justified for this solution and briefly explain your reasoning.