The molecule among the following having the highest dipole moment is:

1. CO2
2. HI
3. H2O
4. SO2

HINT: If the molecule is symmetrical then its dipole moment is zero.

Explanation:

CO2 being symmetrical has zero dipole moment.
Among HI, SO2, and H2O dipole moment is highest for H2O as in it the central atom contain 2 lone pairs. Also the polarity difference between H and O is more as compared to H and S.