Question

The molecule ${\mathrm{CO}}_2$is nonpolar, but $\mathrm{CO}$ is a polar molecule. Explain.

Short answer

Due to electronegativity difference between carbon and oxygen atom ${\mathrm{CO}}_2$ is nonpolar, but $\mathrm{CO}$ is a polar molecule.

Step-by-step solution

Given information

We are given ${\mathrm{CO}}_2$ is nonpolar, but $\mathrm{CO}$ is a polar molecule

Simplify

Because the electronegativities of carbon and oxygen differ from each other, electrons are not shared equally between the two atoms.
However, because ${\mathrm{CO}}_2$geometry is linear, the two bond dipole moments cancel out, leaving no net molecule dipole moment.
The molecule is thus non-polar.