Question

Knowing that 1 mol of a certain monoprotico acid, HX, contained in 1 litre aqueous solution, this 50% ionized, point the value of its ionization constant.

Answer 1

(HX) = 1 mol/L = 1 M
50% ionized means H^+ = 0.5M and X^- = 0.50
........HX ==>H^+ + X^-
I......1.0....0.....0
C......-0.5...0.5..0.5
E.....0.5....0.5...0.5

Plug the E line into the Ka expression and evaluate Ka.
Post your work if you get stuck.