Question

Which contains hydrogen bonds?
(a) \[HF\]
(b) \[HCl\]
(c) \[HBr\] \[\]
(d) \[HI\]

Answer 1

Hint: The hydrogen bond is formed between more electronegative elements and hydrogen atoms such as fluorine, oxygen, nitrogen, etc.,

Complete Step by Step Solution:
When a hydrogen atom is connected to highly electronegative elements then the formation of a hydrogen bond occurs. During the formation of hydrogen bonds, the electronegative atom has a partial negative charge whereas the hydrogen atom possesses a partial positive charge.

The main reason for the hydrogen bond is dipole-dipole interaction.
Type of hydrogen bond
Intermolecular hydrogen bond
When the hydrogen bond exists between two molecules is called an intermolecular hydrogen bond. Such a type of hydrogen bond is found in a carboxylic acid (Image 1).

Image: Intermolecular hydrogen bond in a carboxylic acid.

Intramolecular hydrogen bond: When the formation of a hydrogen bond occurs in the same molecule then it is called an intramolecular hydrogen bond. Such a type of hydrogen bonding can be seen in nitro phenol (Image 2).

Image: Intramolecular hydrogen bond in nitrophenol.

As to the definition hydrogen bond is formed between the hydrogen atom and a more electronegative atom. Therefore, in the question, the fluorine atom is more electronegative than chlorine, bromine, and iodine. Hence the \[HF\] will contain a hydrogen bond.

Note: The hydrogen bond also increases the melting and boiling points of the compounds. The hydrogen bond also increases the solubility of compounds. The hydrogen bonding also increases the viscosity of the compounds. Hydrogen bonding is also present in nucleic acids. Which helps to bind two strands together. The folding in protein is arise due to hydrogen bonding.