Step 1:

The percent ionization is 50 %.

k_a for HF is .

The chemical equation is .

The initial concentration of the [HF] is y M.

Let us consider change in the concentration:  , then .

Initial Amount
Change in Amount
Equilibrium amount			\ \

Step 2:

Percentage ionization :

Step 3:

Acid ionization factor .

Substitute in the above equation.

The initial concentration of the [HF] is M.

Solution:

The initial concentration of the [HF] is M.