In the following question, an Assertion (A) is followed by a corresponding Reason (R). Use the following keys to choose the appropriate answer.
Assertion : The `HF_2^(-)` ion exists in the solid state and also in the liquid state but not in aqueous solution.
Reason : The magnitude of hydrogen bonding in between HF molecules is weaker than that in between HF and `H_2O` molecules. : If both (A) and (R) are correct and (R) is the correct explanation of (A)., If both (A) and (R) are correct, but (R) is not the correct explanation of (A)., If (A) is correct, but (R) is incorrect., If both (A) and (R) are incorrect.

Options

A. If both (A) and (R) are correct and (R) is the correct explanation of (A).
B. If both (A) and (R) are correct, but (R) is not the correct explanation of (A).
C. If (A) is correct, but (R) is incorrect.
D. If both (A) and (R) are incorrect.

Answer

A

Explanation

`DeltaH` for H-F-H-F hydrogen bonding is only 20-23 kJ `mol^(-1)` where as that for H-F-H-O-H is 40-45 kJ `mol^(-1)`. In aqueous solution `HF_2^(-)` ions are dissociated as `HF_2^(-) +3H_2O rarr 2H_3OF+OH^(-)`
`H_3OF` contain `F^(-)` ion bonded to proton with a delocalised charge.