Question

HF is weak acid in comparison to HBr, HCl and HI due to

• A. Weak van der Waals force
• B. Hydrogen bonding
• C. Back bonding
• D. High electronegativity of ‘F’

Answer 1

The correct option is B Hydrogen bonding

The presence of Hydrogen bonding in HF makes it a much weaker acid than HBr, HCl and HI. This bonding makes the abstraction of protons or $H^{+}$ more difficult as compared to the other Hydrogen Halides in solution. Do note that although the $Cl$ in $HCl$ is comparatively highly electronegative, there doesn't seem to be any Hydrogen bonding. In general, a hydrogen bond may be defined as the electrostatic attraction between polar groups that occurs when a Hydrogen atom bound to a highly electronegative atom such as nitrogen (N), oxygen (O) or fluorine (F) experiences attraction to some other nearby highly electronegative atom.

Thus HF is weak acid compared to HBr, HCl and HI.