Hydrofluoric acid, HF, is a weak acid. Which of the following is the correct expression for the K_a of hydrofluoric acid? A) [H₃O⁺][HF]/[F-] B) [HF]/[ H₃O⁺][F-] C) [H₃O⁺][F-]/[HF] D) [HF][F-]/[ H₃O⁺]

Question

Quizplus · Accepted Answer

The K_a expression for a weak acid is [A-][H+]/[HA], where A- is the conjugate base and HA is the acid. In the case of hydrofluoric acid, A- is F- (fluoride ion) and HA is HF (hydrofluoric acid). Therefore, the correct expression is [F-][H+]/[HF], which can be written as [H₃O⁺][F-]/[HF].

Hydrofluoric Acid, HF, Is a Weak Acid