The salt KHF2 is stable but KHCl2 is not known under ordinary conditions. This is because

F- is small and highly electronegative, so it forms a very strong F-H...F- hydrogen bond in HF2-

KCl has a lower lattice energy than KF

F- is small and highly electronegative, so it forms a very strong F-H...F- hydrogen bond in HF2-

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JEE Advanced levelSingle correct optionDifficulty 3 of 3cb216

The salt $KHF X_{2}$ is stable but $KHCl X_{2}$ is not known under ordinary conditions. This is because

A $HCl$ is a weaker acid than $HF$
B $Cl X^{-}$ is smaller than $F X^{-}$
C $KCl$ has a lower lattice energy than $KF$
D $F X^{-}$ is small and highly electronegative, so it forms a very strong $F - H \cdot \cdot \cdot F X^{-}$ hydrogen bond in $HF X_{2} X^{-}$

Answer: D

The

HF X_{2} X^{-}

ion has a symmetrical, exceptionally strong hydrogen bond, which supplies the energy to stabilise the salt. Chlorine is larger and less able to form such a bond, so the corresponding

HCl X_{2} X^{-}

is not stable. The statement that

Cl X^{-}

is smaller than

F X^{-}

or that

HCl

is a weaker acid is false.

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The salt KHFX2​ is stable but KHClX2​ is not known under ordinary conditions. This is because

Answer: D

More questions on Hydrogen bonding and intermolecular forces

The salt $KHF X_{2}$ is stable but $KHCl X_{2}$ is not known under ordinary conditions. This is because