Question

Explain why the enthalpies of vaporization of the following substances increase in the order CH4 < NH3 < H2O, even though all three substances have approximately the same molar mass.

Answer 1

Step-by-step explanation:

More is the intermolecular forces present between the molecules of a substance more will be the boiling point of the substance.

Since, water is able to form hydrogen bonding and it also have dipole-dipole interaction as these are stronger than the forces present in ammonia. Hence, boiling point of water is greater than the boiling point of
`NH_(3)`.

In
`CH_(4)`, there are only dispersion forces present in it and these forces are weakest intermolecular forces.

As a result, the enthalpies of vaporization of the following substances increase in the order
`CH_(4) < NH_(3) < H_(2)O`.