AIIMS 2019 Chemistry Acidic Strength MCQ Question

The order of acidic nature for the given organic compounds indicates that trifluoroacetic acid (F₃C–COOH) is the strongest acid, followed by benzoic acid (C₆H₅COOH), acetic acid (CH₃COOH), and propanoic acid (CH₃CH₂COOH). Since pKₐ values are inversely proportional to acidity, the corresponding order of pKₐ values will be the reverse: propanoic acid has the highest pKₐ, followed by acetic acid, benzoic acid, and trifluoroacetic acid with the lowest pKₐ. Therefore, the correct order of pKₐ values is 4 > 3 > 2 > 1, which is not listed in the options provided, making option B correct as it indicates that the other options are not applicable.