Step 1:

The concentration of the [HF] is 0.100 M.

k_a for HF is .

The chemical equation is .

Let us consider change in the concentration:  , then .

Initial Amount
Change in Amount
Equilibrium amount			\ \

Step 2:

Acid ionization factor .

\ \

Concentration cannot be negative.

Step 3:

Percentage ionization :

.

Solution:

.