What does an increase in Ka indicate about a weak acid?

An increase in the acid dissociation constant (Ka) for a weak acid indicates that the acid is dissociating more in solution, which means it produces more hydrogen ions (H⁺). This increased dissociation reflects that the weak acid is behaving more like a strong acid.

When a weak acid has a higher Ka, it suggests that the equilibrium of the dissociation reaction lies further to the right, favoring the formation of hydronium ions (H₃O⁺) and the conjugate base. Therefore, even though the substance is still classified as an acid and may not be as strong as strong acids (which completely dissociate), an increase in Ka indicates it is acting more strongly than at lower values of Ka.

As for the options that do not align with this conclusion, an increase in Ka does not imply that the weak acid becomes a strong acid in a categorical sense, but rather it is behaving more strongly under the conditions specified. Likewise, the pH decreases as the concentration of H⁺ increases with a higher Ka, not increases. The concentration of the conjugate base is also not guaranteed to simply increase due to a higher Ka since it depends on the system's specific conditions and concentrations at equilibrium.