Which of the following molecules has the largest dipole moment?

• A. HCl
• B. NH3
• C. CO
• D. O2

Answer: (B)

Verified step by step guidance

1. Recall that the dipole moment of a molecule depends on both the difference in electronegativity between atoms and the molecular geometry, which affects how individual bond dipoles add up.
2. Examine each molecule's bond polarity by considering the electronegativity difference between the atoms: HCl, NH3, CO, and O2.
3. Consider the molecular geometry: NH3 has a trigonal pyramidal shape with a lone pair on nitrogen, which creates a net dipole moment because the bond dipoles do not cancel out.
4. Note that O2 is a nonpolar molecule because it consists of two identical atoms sharing electrons equally, so its dipole moment is zero.
5. Compare the overall dipole moments qualitatively: although CO has a polar bond, NH3's geometry and bond polarities combine to give it the largest net dipole moment among the options.