Question

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

Answer 1

Hint: 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.