To analyze the statements regarding hydrochloric acid (HCl) and acetic acid (CH₃COOH), we should consider their properties as a strong acid and a weak acid, respectively.
A. The pH of a solution of hydrochloric acid must be less than the pH of a solution of acetic acid.
- This statement is generally correct if the concentrations of both acids are equal. Hydrochloric acid is a strong acid and fully dissociates in solution, leading to a lower pH than an equivalent concentration of acetic acid, which only partially dissociates.
B. If the initial concentration of each acid is the same, then acetic acid will produce more H₃O⁺ ions than hydrochloric acid.
- This statement is incorrect. Hydrochloric acid will produce more H₃O⁺ ions than acetic acid at the same initial concentration since it completely dissociates while acetic acid only partially dissociates.
C. A solution of hydrochloric acid at equilibrium will have a greater concentration of solute than a solution of acetic acid at equilibrium.
- This statement is incorrect in terms of the total concentration of solute. The concentrations of acid molecules themselves may differ due to complete versus partial dissociation, where HCl will not have any undissociated molecules at equilibrium, while CH₃COOH will have some remaining.
D. The dissociation constant for hydrochloric acid is greater than the dissociation constant for acetic acid.
- This statement is correct. Hydrochloric acid is a strong acid and has a very high dissociation constant (effectively infinite as it fully dissociates), while acetic acid has a much smaller dissociation constant (around 1.76 × 10⁻⁵).
Based on the evaluations:
- A and D are correct.
- B and C are incorrect.
If only one correct statement is to be selected, D is a clear and fundamental characteristic of these acids.