Question

if a solid line represents a covalent bond and a dotted line represents intermolecular attraction, which of the choices shows a hydrogen bond?
h₃n······h - o - h
h₂o······h - ch₃
h₄c······h - f
h - h

Explanation:

Hydrogen bonding occurs when a hydrogen atom is covalently bonded to a highly electronegative atom (such as N, O, or F) and is attracted to another electronegative atom. In the first option \(H_3N\cdots H - O - H\), the hydrogen atom in \(H - O - H\) (water) is attracted to the nitrogen atom in \(H_3N\) (ammonia). Nitrogen and oxygen are highly electronegative.

In the second option \(H_2O\cdots H - CH_3\), carbon in \(CH_3\) is not highly electronegative enough to form a hydrogen bond with the hydrogen in water.

In the third option \(H_4C\cdots H - F\), carbon in \(H_4C\) (methane) is not highly electronegative enough to form a hydrogen bond with the hydrogen in \(HF\).

In the fourth option \(H - H\), there is no electronegative atom involved, so it is just a covalent bond between two hydrogen atoms and no hydrogen bonding.

Answer:

\(H_3N\cdots H - O - H\)