Calculate the pH of a solution that is 0.50 M in HF (K_a = 7.2 $\times$ 10^-⁴)and 0.95 M in NaF.

Question

Quizplus · Accepted Answer

HF is a weak acid, and NaF is its conjugate salt, so this is a buffer solution. First, we need to calculate the pH of the buffer solution assuming HF completely dissociates into H+ and F-.

Using the Henderson-Hasselbalch equation:

pH = pKa + log([A-]/[HA])

where pKa is the acid dissociation constant of HF, [A-] is the concentration of F- (which comes from NaF), and [HA] is the concentration of undissociated HF.

pKa for HF is 3.14 (given)

[A-] = 0.95 M (given)

[HA] = 0.50 M (initial concentration of HF before any dissociation)

plugging it all in, we get:

pH = 3.14 + log(0.95/0.50) = 3.42

Therefore, the answer is B.

Calculate the PH of a Solution That Is 0 ×\times× 10-4)and 0

Calculate the PH of a Solution That Is 0 $\times$ 10^-⁴)and 0