For equal-volume samples of 0.10 M HF(aq) and 0.10 M HCl(aq)
CHEMISTRY · Single correct · A Level · Chemistry · Acids and bases · Acids and bases
Problem
For equal-volume samples of 0.10 M HF(aq) and 0.10 M HCl(aq), the initial pH of the HF solution is higher. Which of the following best accounts for this observation?
(a) HF ionizes only partially in water because its acid dissociation constant, Ka, is much smaller than 1.
(b) Because fluorine is highly electronegative, HF actually dissociates more than HCl; however, the F− ions immediately re-combine with H3O+, so the measured pH is higher.
(c) HF produces fewer hydronium ions because most of the fluoride ions subsequently undergo hydrolysis to produce hydroxide ions that neutralize the acid.
(d) HF donates fewer protons because, during pH measurement, its 0.10 M solution is effectively diluted more than the 0.10 M HCl solution, lowering the hydronium-ion concentration.