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JEE Main levelSingle correct optionDifficulty 2 of 3ph026

$HF$ is a much weaker acid than $HCl$ in water. The main reason is

Athe H-F bond is non-polar
Bthe H-F bond dissociation enthalpy is very high (about 568 kJ/mol against 431 kJ/mol for H-Cl)
Cfluorine is less electronegative than chlorine
Dthe H-F bond is longer than the H-Cl bond

Answer: B

Ionisation of HX in water is opposed by the energy needed to break the H-X bond. The H-F bond is the shortest and strongest, and the high enthalpy outweighs the large hydration enthalpy of

F X^{-}

. Fluorine is the most electronegative, so the other options are false.

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