Question

Which one has strongest hydrogen bond?

• A. F - H - - - F
• B. F - H - - - O
• C. S - H - - - F
• D. O - H - - - O

Answer 1

Answer: (A)

Hydrogen bonds are usually encountered in hydrogen fluoride, water, ammonia, alcohols, carboxylic acids and amines.
Greater the electronegativity and small the size of the atom $(F,O,N)$, the stronger is the hydrogen bond.
So, the relative order of energies of hydrogen bonds is:
$H-F---H>H-O---H>H-N---H$
So, $F-H---F$ has strongest hydrogen bond.