Calculate [H⁺] in a solution that is 0.30M in NaF and 0.46 M in HF. (K_a = 7.2 × 10^-4) A) 1.2 × 10^-4 M B) 5.7 × 10^-3 M C) 231.5 × 10^-2 M D) 4.7 × 10^-4 M E) 0.46 M

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Quizplus · Accepted Answer

The concentration of [HS^(-)] in the solution can be calculated using the formula for the dissociation of HF in the presence of a common ion (F^- from NaF). The equilibrium expression for HF dissociation is K_a = [H^+][F^-]/[HF], where K_a is the acid dissociation constant for HF. Given K_a (7.2 × 10^-4) and the concentrations of HF (0.46 M) and F^- (0.30 M from NaF), we can solve for [H^+]. Assuming x is the concentration of H^+ produced, the equilibrium expression becomes 7.2 × 10^-4 = (x)(0.30+x)/(0.46-x). Since x is small compared to 0.30 and 0.46, it can be approximated that 7.2 × 10^-4 ≈ (x)(0.30)/0.46. Solving for x gives a value in the order of 10^-3, making choice B the closest match.

Calculate [H+] in a Solution That Is 0

Calculate [H⁺] in a Solution That Is 0