Question

Among $HCl\,,\,{H_2}O\,$ and $N{H_3}$ ,which has a higher boiling point and why?

Answer 1

The boiling point also referred to as B.P is a temperature at which the vapour pressure of the liquid equals the external pressure surrounding the liquid. The boiling point (B.P) of a liquid depends upon the atmospheric pressure. The factor that influences the B.P is the strength of intermolecular forces., like ionic bonding, hydrogen bonding, etc.

Complete step by step answer:
The electrostatic force of attraction between the Hydrogen and the electronegative atom such as nitrogen, oxygen, fluorine, etc., is called Hydrogen bonding. In such bonds, the hydrogen acts as a donor and the electronegative element acts as an acceptor. The Hydrogen bond is having a special type of interaction i.e., dipole-dipole interaction.
Hydrogen bond strength ranges from $4{{ }}kJ$ - $50{{ }}kJ{{ }}mo{l^{ - 1}}$ of hydrogen bonds.
From $HCl\,,\,{H_2}O\,$ and $N{H_3}$ ,
${H_2}O\,$ is having the highest boiling point.

The ${H_2}O\,$ is hydrogen bonding. But even in $N{H_3}$ there is hydrogen bonding, since it's weaker than ${H_2}O\,$ due to the less electronegativity of nitrogen than oxygen.
The main reason ${H_2}O\,$ is having great hydrogen bond because ${H_2}O\,$ is having bent shape structure that allows for the greater interaction with the adjacent ${H_2}O\,$ molecules.
The ${H_2}O\,$ is having more hydrogen bonding than $HF$ . Even though the Fluorine is having higher electronegativity than Oxygen, the important thing to be noted is that $HF$ can form two hydrogen bonding whereas, ${H_2}O\,$ can form four hydrogen bonding. Due to this reason, $HF$ is having less boiling point than ${H_2}O\,$.
When we see the $HCl$ , it lacks the ability to form hydrogen bonding. This is due to the size of $Cl$ that hides the hydrogen to form intermolecular hydrogen bonding. Since hydrogen is very small.
${H_2}O{{ }} > {{ }}N{H_3} > {{ }}HCl$

Note: In ${H_2}O\,$, Oxygen has two lone-pairs. In $N{H_3}$ , nitrogen has one lone-pair. So, ${H_2}O\,$ form four $H - {{ }}bonds$ whereas, in the case of $N{H_3}$ ,it forms two $H - {{ }}bonds$. In the case of $HCl$ we saw that chlorine hides the hydrogen due to their sizes. That’s the reason, ${H_2}O\,$ is more stable and it needs more energy to break the bond. As the hydrogen bond increases the compound is having more boiling point.