Question

Since the atoms in a water molecule do not have equal ability to attract charges, we say that a water molecule has a dipole moment. That means oxygen has a little more electronegativity than hydrogen. Which statement correctly describes the dipole moment of a water molecule?

1) The dipole moment of a water molecule is zero.
2) The dipole moment of a water molecule is positive.
3) The dipole moment of a water molecule is negative.
4) The dipole moment of a water molecule cannot be determined.

Answer 1

The dipole moment of a water molecule points from the hydrogen atoms towards the more electronegative oxygen atom, indicating a net negative direction owing to the larger partial negative charge at the oxygen end.

Step-by-step explanation:

The dipole moment of a water molecule is a result of its polar nature, where the oxygen atom has a higher electronegativity than the hydrogen atoms. This difference in electronegativity leads to an uneven distribution of electronic charge, with oxygen having a partial negative charge (δ-) and hydrogen having a partial positive charge (δ+). The molecular structure of water is bent due to the lone pairs of electrons on the oxygen atom, and as a result, the individual O-H bond dipoles do not cancel each other out, instead they add up to create a net dipole moment that points from the hydrogen atoms towards the oxygen atom. This net dipole moment indicates the separation of charge within the molecule, meaning the correct statement describing the dipole moment of a water molecule is that it has a net negative direction (if we consider the direction pointing towards the more negative end as being negative).