Determine the [F-] of the following solution. Initial concentrations are given. [HF] = 1.296 M, [NaF] = 1.045 M, Ka for HF is 6.6 × 10^-4 A) 1.046 M B) 2.344 M C) 5.3 × 10^-4 M D) 8.2 × 10^-4M E) 0.251 M

Question

Quizplus · Accepted Answer

First, we need to write out the equilibrium equation for HF dissociating in water:
HF + H2O ⇌ H3O+ + F-
Ka = [H3O+][F-] / [HF]
We can make an ICE table to determine the equilibrium concentrations:
HF    +    H2O ⇌   H3O+    +    F-
I:        1.296 M        1.045 M       0 M             0 M
C:       -x                 -x             +x            +x
E:     1.296-x       1.045-x      x               x
We can substitute these concentrations into the Ka expression and solve for x (the concentration of [F-]):
6.6 × 10^-4 = (x)(x) / (1.296 - x)
Solving for x gives us x = 1.046 M, which is the concentration of [F-]. Therefore, the correct answer is A.

Determine the [F-] of the Following Solution