Question

Ozone has a dipole moment of 0.53 D. Carbon dioxide has a dipole moment of zero, even though C-O bonds are more polar than O-O bonds. Explain this apparent contradiction.

Short answer

Each C-O bond in carbon dioxide is polar, in spite of this carbon dioxide molecule has zero dipole moment. Because the two C-O bond dipoles in carbon dioxide are equal in magnitude and oriented at 180° to each other, so they cancel. Whereas in ozone the electrons are not shared equally among the oxygen atoms and it has bent structure. The major contribution in the dipole moment of ozone is due to the lone pair in the directional orbital of the central oxygen atom therefore it has net dipole moment.

Step-by-step solution

Step 1:

Molecular dipole moment is the vector combination of which can be regarded as individual bond dipole moments. The dipole moment of a molecule is therefore thevector sum of the dipole moments of the individual bonds in the molecule. If the individual bond dipole moments cancel one another, there is no net dipole moment.

Step 2:

Symmetry can be used to determining, if a molecule has a dipole moment. If a molecule is completely symmetric, the dipole moment vectors on each molecule will cancel each other out, making the molecule nonpolar.