The correct statement is:
The dissociation constant for hydrochloric acid is greater than the dissociation constant for acetic acid.
Hydrochloric acid (HCl) is a strong acid that completely dissociates in solution, whereas acetic acid (CH₃COOH) is a weak acid that only partially dissociates. As a result, the dissociation constant (Ka) for hydrochloric acid is effectively infinite, while the Ka for acetic acid is much smaller, reflecting its weak acidic nature.
Let's clarify the incorrect options:
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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 not necessarily true, as it depends on the initial concentrations. However, since HCl fully dissociates, it would typically lead to a higher concentration of H⁺ ions compared to acetic acid at the same initial concentration.
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If the initial concentration of each acid is the same, then acetic acid will produce more H₃O⁺ ions than hydrochloric acid.
- This statement is false because hydrochloric acid fully dissociates, contributing more H₃O⁺ ions compared to the weakly dissociated acetic acid.
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The pH of a solution of hydrochloric acid must be less than the pH of a solution of acetic acid.
- This is true under equal initial concentrations but depends on specific concentrations as weak acids like acetic acid can have less H⁺ concentration at certain lower concentrations.
Thus, the most definitive and correct statement regarding the nature of these acids is the comparison of their dissociation constants.
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