Question

Which of the following hydrogen bonds is the strongest?
A) $F - H...F$
B) $O - H...O$
C) $S - H...F$
D) $F - H...O$

Answer 1

As we already know that the electronegativity of the element attached to hydrogen is the most important factor in determining the strength of hydrogen bonding. Also as the electronegativity increases the hydrogen bonding increases or becomes stronger.

Complete solution:
We know that hydrogen bonding is a special type of bonding which is primarily an electrostatic force of attraction between a hydrogen atom and more electronegative atom or group such as nitrogen, fluorine, oxygen and other very electronegative atoms.
We also know that electronegativity is a measure of the tendency of an atom to attract a shared pair of electrons or a bonding pair of electrons.
So, the strength of hydrogen bond depends upon the interaction which is coulombic between the electronegativity of the attached atom and hydrogen.
Now, among the following given elements the electronegativity order is as followed:
$F > O > S$
So, we can say that the fluorine is the most electronegative element among the following given elements.Therefore, the strongest hydrogen bond will be formed by the $F - H...F$.

Therefore,the correct option is (A).

Note: Remember that the hydrogen bonding is of two types that is Intermolecular hydrogen bonding and Intramolecular hydrogen bonding. Intramolecular hydrogen bonding is stronger than intermolecular hydrogen bonding. Also remember the electronegativity of the elements where fluorine is most electronegative as compared to sulphur, nitrogen and oxygen.