Paper: CSIR-NET December 2019 · Subject: Inorganic Chemistry · Chapter: Acids and Bases · Topic: Acid and Bases – General · Marks: 2 · Difficulty: Medium
Among $\mathrm{SO_2(OH)F}$, $\mathrm{CH_3CO_2H}$, LiF and $\mathrm{H_2O}$, the compound(s) which behave(s) as a base in liquid HF is/are
(a)$\mathrm{CH_3CO_2H}$ and LiF only
(b)LiF only
(c)$\mathrm{SO_2(OH)F}$ and LiF only
(d)$\mathrm{CH_3CO_2H}$, LiF and $\mathrm{H_2O}$
Answer
Answer: D ✓ checked by 4AB · confidence high
The source book printed no answer; this one was worked out and checked — see the explanation.
Explanation
Liquid HF is a very strong protonating solvent. CH₃CO₂H is protonated ([CH₃C(OH)₂]⁺ + HF₂⁻), LiF gives F⁻ which forms HF₂⁻, and H₂O is protonated to H₃O⁺: all three behave as bases. SO₂(OH)F (fluorosulfuric acid) is stronger than HF and behaves as an acid.