Question

In which of the following, intermolecular forces are the weakest?
(a)- $C{{H}_{3}}C{{H}_{2}}OH$
(b)- $N{{H}_{3}}$
(c)- ${{H}_{2}}O$
(d)- $C{{O}_{2}}$

Answer 1

Hint: Intermolecular forces are of many types like hydrogen bonding, dipole-dipole interaction, van der Waal forces, covalent bonding, London dispersion forces, etc and these forces are responsible for the formation and stability of the molecule in solid, liquid, and gaseous form. Mostly the compounds that are able to form hydrogen bonding have strong intermolecular forces.

Complete answer:
We know that there are three types of states of matter, i.e., solids, liquids, and gases, and these states of matter are distinguished due to the intermolecular forces between the molecules. The intermolecular forces are highest in the solids and the intermolecular forces are lowest in the gases.
Intermolecular forces are of many types like hydrogen bonding, dipole-dipole interaction, van der Waal forces, covalent bonding, London dispersion forces, etc and these forces are responsible for the formation and stability of the molecule in solid, liquid, and gaseous form.
In $C{{H}_{3}}C{{H}_{2}}OH$, hydrogen bonding is present as the intermolecular forces because there is an electronegative atom present in ethanol, i.e., oxygen atom which has the ability to form hydrogen bonding with the hydrogen atom of other molecules.
In $N{{H}_{3}}$, hydrogen bonding is present as the intermolecular forces because there is an electronegative atom present in ammonia, i.e., nitrogen atom which has the ability to form hydrogen bonding with the hydrogen atom of other molecules.
In ${{H}_{2}}O$, hydrogen bonding is present as the intermolecular forces because there is an electronegative atom present in water, i.e., oxygen atom which has the ability to form hydrogen bonding with the hydrogen atom of other molecules.
In $C{{O}_{2}}$, dispersion forces are present because there is no electronegative atom present in the molecule.
So, hydrogen bonding is stronger bonding than the dispersion forces due to which weakest force will be present in $C{{O}_{2}}$.

Therefore, the correct answer is an option (d).

Note:
From the given options: ethanol, ammonia, and water are liquids while carbon dioxide is gas because as the strength of the intermolecular forces increases the state of the compounds changes to solid or liquid form.