Which one among the following statements regarding acids and bases is

Which one among the following statements regarding acids and bases is not correct ?

A conjugate base of a strong acid is a weak base.
In aqueous solution, the hydroxide ion is hydrated to give several ionic species like H₃O₂⁻, H₅O₃⁻ and H₇O₄⁻ etc.
AlCl₃ is an electron deficient compound, and can act as a Lewis base.
Fluoride ion acts as a Lewis base as it can donate any one of its four electron lone pairs.
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UPSC Geoscientist – 2024
The statement “AlCl₃ is an electron deficient compound, and can act as a Lewis base” is not correct.
AlCl₃ is electron deficient because the central aluminum atom has only six valence electrons (an incomplete octet). According to the Lewis definition, substances that can accept an electron pair are Lewis acids, while substances that can donate an electron pair are Lewis bases.
Since AlCl₃ is electron deficient, it readily accepts electron pairs from other molecules (like water, ammonia, or chloride ions) to complete its octet. Therefore, AlCl₃ acts as a Lewis acid, not a Lewis base. Statement A is correct (e.g., Cl- from HCl is a weak conjugate base). Statement B is correct regarding the hydration of hydroxide ions. Statement D is correct; a fluoride ion has four lone pairs and can donate one to act as a Lewis base.
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