The Following Question Refers to a Solution That Contains 1 $\times$

Multiple Choice

The following question refers to a solution that contains 1.99 M hydrofluoric acid,HF (K_a = 7.2 $\times$ 10^-4) ,and 3.00 M hydrocyanic acid,HCN (K_a = 6.2 $\times$ 10^-10) . Determine the [CN^-] at equilibrium.

A) 1.9 $\times$ 10^-9 M
B) 3.8 $\times$ 10^-2 M
C) 4.9 $\times$ 10^-8 M
D) 6.2 $\times$ 10^-10 M
E) none of these