Question

The premise that H2S has a greater dipole moment than H2O is incorrect. The dipole moment of H2O is significantly greater than that of H2S.

The dipole moment of a molecule depends on the polarity of its bonds and its molecular geometry.

1. Electronegativity: Oxygen (electronegativity ≈ 3.44) is considerably more electronegative than Sulfur (electronegativity ≈ 2.58). Hydrogen has an electronegativity of about 2.20.

   • The electronegativity difference in O-H bonds (3.44 - 2.20 = 1.24) is much larger than in S-H bonds (2.58 - 2.20 = 0.38).
   • This means the O-H bonds are much more polar than the S-H bonds, leading to larger partial charges on the atoms in H2O.

2. Molecular Geometry: Both H2O and H2S are bent (V-shaped) molecules due to the presence of two lone pairs on the central atom (Oxygen or Sulfur). In a bent molecule, the bond dipoles do not cancel out and add up vectorially to give a net molecular dipole moment.

3. Resultant Dipole Moment: The greater polarity of the O-H bonds in water, combined with its bent geometry, results in a larger net molecular dipole moment.

   • Dipole moment of H2O is approximately 1.85 Debye (D).
   • Dipole moment of H2S is approximately 0.97 Debye (D).

Therefore, H2O has a greater dipole moment than H2S.

Answer 1

The dipole moment of H2O is greater than H2S.

Answer 2

The dipole moment of H2O is greater than H2S primarily due to the higher electronegativity of Oxygen compared to Sulfur. This makes the O-H bonds more polar than S-H bonds. Although both molecules are bent, the greater bond polarity in H2O leads to a larger net molecular dipole moment.