Why is CO_2 a nonpolar molecule, whereas CO is a polar molecule?

1 Answer
anor277
Jan 23, 2017

Consider the vector sum of the individual bond dipoles........

Explanation:

The C-O bond in both gases is polar to a certain, limited extent. ""^(+delta)C-=O^(delta-) has some polarity; on the other hand, for ""^(delta-)O=^(delta+)C=O^(delta-), the vectors of the bond dipoles clearly sum to ZERO.

This polarity is not reflected in the boiling points of the 2 gases, -191.5^@ for CO at 1*atm, versus a normal sublimation point of -78^@C for carbon dioxide, however, carbon dioxide is a bigger molecule, with extra dispersion forces.

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