Question

The correct order of increasing intermolecular hydrogen bond strength is

• A. \(HCN < H_2O < NH_3\)
• B. \(HCN < CH_4 < NH_3\)
• C. \(CH_4 < HCN < NH_3\)
• D. \(CH_4 < NH_3 < HCN\)

Answer 1

The Correct Option is C

To determine the correct order of increasing intermolecular hydrogen bond strength among the given substances, we must first understand the concept of hydrogen bonding and the factors that contribute to its strength.

Hydrogen bonds are a type of strong dipole-dipole interaction that occurs in molecules where hydrogen is directly bonded to highly electronegative atoms such as fluorine (F), oxygen (O), or nitrogen (N). The strength of hydrogen bonds depends on a few key factors:

• The electronegativity of the atom to which hydrogen is bonded. The more electronegative the atom, the stronger the hydrogen bond.
• The availability of lone pairs on the electronegative atom that can participate in hydrogen bonding.

Now, we will analyze each of the substances given in the options:

1. CH_4 (Methane): Methane does not participate in hydrogen bonding because carbon (C) is not electronegative enough to allow the formation of hydrogen bonds. Thus, it has the weakest intermolecular interactions among the options.
2. HCN (Hydrogen cyanide): Although HCN has nitrogen, it generally forms weaker hydrogen bonds compared to NH₃ because the structure limits the availability of the lone pair for hydrogen bonding, and carbon is not strongly electronegative.
3. NH_3 (Ammonia): In ammonia, nitrogen is directly bonded to hydrogen, and the molecule has a lone pair that can participate in hydrogen bonding. This makes ammonia capable of forming relatively strong hydrogen bonds.

Based on this analysis, the correct order of increasing intermolecular hydrogen bond strength is:

CH_4 < HCN < NH_3

This means that methane has the weakest interactions, followed by hydrogen cyanide, and ammonia has the strongest hydrogen bonding capabilities among the given substances.

Thus, the correct answer is: CH_4 < HCN < NH_3