Question

Does ${{\text{H}}_{\text{2}}}{\text{O}}$have a greater dipole moment than ${{\text{H}}_{\text{2}}}{\text{S}}$?

Answer 1

Let us, first of all, have a brief knowledge about dipole moments. Dipole moments occur when there is a separation of charges. Dipole moments are caused by changes in electronegativity and can occur between two ions in an ionic bond or between atoms in covalent bonding. The dipole moment increases with the difference in electronegativity. The size of the dipole moment is also determined by the distance between the charge separations.

Complete answer:
We know that between ${{\text{H}}_{\text{2}}}{\text{O}}$ and ${{\text{H}}_{\text{2}}}{\text{S}}$, a hydrogen atom is common. In the first molecule, two oxygen atoms are bonded to hydrogen and in the second, two sulphur atoms are bonded to the hydrogen atom.
So, when we compare the dipole moment of these two molecules, it will depend on the electronegativity of oxygen and sulphur. Electronegativity is defined as the tendency of an atom in a molecule to attract the shared pair of electrons towards itself.
Because oxygen is more electronegative than sulphur, the water molecule should have higher polarization of electron density, or charge separation, than the hydrogen sulphide molecule.
Thus, ${{\text{H}}_{\text{2}}}{\text{O}}$ has a greater dipole moment than ${{\text{H}}_{\text{2}}}{\text{S}}$.

NOTE:
It can further be noted that a dipole moment is created when electrons are shared unequally among atoms in a molecule. This happens when one atom is more electronegative than another, causing that atom to pull harder on the shared pair of electrons, or when one atom has a lone pair of electrons and the electronegativity vector points in the same direction. Oxygen has a partial negative charge in water, while each of the hydrogens has a partial positive charge.