Final answer:
The degree of ionization of the Ka of the unknown acid is approximately 3.256%.
Step-by-step explanation:
The degree of ionization of an acid can be determined by calculating the concentration of ionized and unionized acid molecules in solution. In this case, the value of [H₃O+] at equilibrium is given as 4.07 x 10⁻³ M when the concentration of the unknown acid is 0.125 M. Since [H₃O+] is a measure of ionization, the degree of ionization can be calculated by dividing the concentration of [H₃O+] by the initial concentration of the acid:
Degree of ionization = [H₃O+]/[HA]
Substituting the given values:
Degree of ionization = (4.07 x 10⁻³ M)/(0.125 M) = 0.03256
Therefore, the degree of ionization of the acid (Ka) is approximately 0.03256, or 3.256%.