Which of the following is a covalent compound containing polar bonds?

a. OCl2.

b. AlCl3.

c. CO2.

OCl₂

Explanation:

To determine whether a covalent compound contains polar bonds you must deal with dipole moments and symmetry.

If a molecule has dipole moments and the charge is not symmetrically distributed then the covalent ompound is polar.

This is the analysis for the given compounds.

First of all, AlCl₃ is an ionic compound, because the difference of electronegativities between Al (a metal) and Cl (a nonmetal) atoms is large enough to gender the formation of ions.

CO₂: since C and O are two nonmetals, with different electronegativities, each C=O bond is polar. Nevertheless, it is a planar molecule (its geometry is O = C = 0), so the molecule is completely symmetric, and the dipole moments of each C=O pair are cancelled. So, this is not a polar molecule.

The structure of OCl₂ is similar to that of water (H₂O). So, it is not planar but bended. The bent geometry is due to the lone pairs on the oxygen. Also, due to steric repulsion between the relatively large chlorine atoms the bond angle is a bit larger than the normal angle. While for the H₂O molecules the bond angle is about 104.45°, it is about 110.9° for OCl₂. Then, being it bended, the dipole moment do not cancel and the molecule is polar.