Which of the following diagrams best represents the net dipole moment of a water (H_2O) molecule?

• A. No arrows shown, indicating no net dipole moment.
• B. An arrow pointing from the midpoint between the hydrogen atoms toward the oxygen atom, indicating a net dipole toward hydrogen.
• C. An arrow pointing from the oxygen atom toward the midpoint between the two hydrogen atoms, indicating a net dipole toward oxygen.
• D. Two arrows of equal length pointing away from the oxygen atom toward each hydrogen atom, with no net dipole.

Answer: (C)

Verified step by step guidance

1. Recall that the dipole moment is a vector quantity that points from the positive end to the negative end of a polar bond or molecule.
2. Identify the electronegativities of the atoms in the water molecule: oxygen is more electronegative than hydrogen, so each O–H bond has a dipole moment pointing from hydrogen (partial positive) toward oxygen (partial negative).
3. Consider the molecular geometry of water, which is bent (angular) with an angle of about 104.5°, meaning the two O–H bond dipoles do not cancel out but combine to give a net dipole moment.
4. Add the two bond dipole vectors vectorially, noting that their resultant points from the midpoint between the hydrogen atoms toward the oxygen atom, indicating the overall dipole moment direction.
5. Conclude that the net dipole moment arrow should point from the oxygen atom toward the midpoint between the two hydrogen atoms, reflecting the molecule's polarity.