Final answer:
To determine the Ka of the weak acid, we can calculate the concentration of H+ ions using the pH, assume complete ionization of the weak acid, and use the equation Ka = [H+]^2 / [HA].
Step-by-step explanation:
To determine the Ka of the weak acid, we can first calculate the concentration of H+ ions in the solution using the pH. The pH of 1.80 corresponds to a H+ concentration of 10^(-pH) = 10^(-1.80). Next, we can assume that the weak acid is completely ionized (100% dissociation). Therefore, the concentration of the weak acid is equal to the concentration of H+ ions. The Ka can be calculated using the equation Ka = [H+]^2 / [HA]. Substituting the known values, we have Ka = (10^(-1.80))^2 / 0.086.