Question

When referring to percent ionization values given in a acid/base table,

how to determine what is the hydrogen ion concentration of a 0.10 mol/L solution of hydrofluoric acid?

Answer 1

The following answers the question but it doesn't involve percent ionization unless you want to calculate it from the Ka values in the table.
HF ==> H^+ + F^-

Use the ICE table.
Initial concentration
Change in conen and
Equilibrium concn.

Iinitial concn:
(HF) = 0.1 M
(H^+) = 0
(F^-) = 0

Change in concn:
(H^+) = +x
(F^-) = +x
(HF) = -x

Equilibrium concn:
(HF) = 0.1-x
(H^+) = 0 + x = x
(F^-) = 0 + x = x

Write the Ka expression. For HF it is
(H^+)(F^-)/(HF) = Ka.
Look up Ka in your tables, plug in the equilibrium concn from above, and solve for x. That is the (H^+).