Question

Among the molecules given below, identify those which are microwave active. Justify your answer.I2, HBr, CO2, CS2, NO​

Answer 1

Answer: NO ( nitric oxide) and HBr ( Hydrogen bromide) are microwave active.

Explanation:

The main criteria for a molecule to be microwave active is possession of a permanent dipole moment, in order to get a rotational spectrum and be microwave active.

Homonuclear molecules are not microwave active , therefore I2 is inactive, CO2 and CS2 have net zero dipole moment ( have equal and opposite dipole moment that gets cancelled out) so only HBr and NO are microwave active molecules.

Answer 2

Among the molecules given below, out of I2, HBr, CO2, CS2, NO, only HBr and NO are microwave active.

The gross selection rule maintains that molecules which are permanently dipolar can be microwave active, such as heteronuclear diatomics like HCL, CO and NO.

Homonuclear molecules do not have a dipole, like I2, O2, hence these are microwave inactive.CO2 and CS2 also do not qualify for having no dipolar moment.