Which of the following are polar molecules?
I. PCl₃
II. H₂O
III. CO₂
IV. BF₃

Question

Which of the following are polar molecules? I. PCl₃ II. H₂O III. CO₂ IV. BF₃

Quizplus · Accepted Answer

A molecule is considered polar if it has a net dipole moment due to the unequal sharing of electrons between atoms. In order for a molecule to be polar, it must also have polar bonds. 
Looking at the given molecular formulas, we can determine the polar bonds, and then determine if the molecule as a whole is polar or nonpolar. 
I. PCl5 is a polar molecule due to the polar P-Cl bonds and the trigonal bipyramidal geometry, which results in a net dipole moment. 
II. H2O is a polar molecule due to the polar H-O bonds and the bent geometry, which results in a net dipole moment. 
III. CO is a nonpolar molecule because the polar C-O bond dipoles cancel out due to the linear geometry of the molecule. 
IV. BF3 is a nonpolar molecule because the polar B-F bond dipoles cancel out due to the trigonal planar geometry of the molecule.

Therefore, only I and II are polar molecules.

Which of the Following Are Polar Molecules