Question

Boiling point of alcohol is higher than that of its corresponding alkane. Why?

Answer 1

Hint: As we know, the boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid, and then it will change into a vapor.

Complete step by step answer:
As the name suggests, alcohol is an organic compound that carries at least one hydroxyl functional group (-OH) which is bound to a carbon atom.

Now let us discuss the properties of alcohol in brief: as we know alcohols are highly soluble in water and this is due to the presence of hydroxyl groups which can form hydrogen bonds with a water molecule.
The solubility of alcohol in water decreases as the length of the hydrocarbon chain increases and this is because it requires more energy to overcome the hydrogen bonds between the alcohol molecules. After all, molecules are more tightly packed together as the size and mass increase.

Now we know that the boiling point of alcohol is always much higher than the boiling point of the corresponding alkane and this is because the intermolecular forces of alcohol are hydrogen bonds, while alkanes with van der Waals forces as their intermolecular forces.

Therefore, it is concluded that boiling point of alcohol is higher than that of alkane.

Note: Remember, do not confuse intermolecular forces with intramolecular forces because intramolecular forces bind together the atoms making up a molecule or compound whereas intermolecular forces are present within the molecules.