Question

The following diagrams represent aqueous solutions of three acids, HX, HY, and HZ. The water molecules have been omitted for clarity, and the hydrated proton is represented as H rather than H3O . (a) Which of the acids is a strong acid? Explain. (b) Which acid would have the smallest aciddissociation constant, Ka? (c) Which solution would have the highest pH?

Answer 1

(a) We can see here that the strong acid in the diagrams is the one that completely dissociates in water, producing a high concentration of hydronium ions (H3O+). HY is a strong acid.

(b) The acid with the smallest acid dissociation constant, Ka, would be the one that undergoes the least dissociation in water. Thus, the acid with the smallest acid dissociation constant, Ka is HZ.

(c) The solution with the highest pH would be the one with the lowest concentration of H+ ions. HX is the solution would have the highest pH

A smaller Ka value indicates weaker acid strength. Looking at the diagrams, it appears that acid HZ would have the smallest Ka. This is because there is a lower concentration of H+ ions compared to the other acids, suggesting a lower degree of dissociation.