Question

The boiling point of H₂O is much higher than that of the analogous molecule H₂S. This is mostly due to?

1) Difference in molecular weight
2) Difference in intermolecular forces
3) Difference in atomic number
4) Difference in electronegativity

Answer 1

The boiling point of H₂O is significantly higher than H₂S due to the presence of strong hydrogen bonds in H₂O, which requires more energy to break compared to the weaker intermolecular forces in H₂S.

Step-by-step explanation:

The boiling point of H₂O is much higher than that of the analogous molecule H₂S mostly due to difference in intermolecular forces, specifically hydrogen bonding. In H₂O, the hydrogen atoms are bonded to a highly electronegative oxygen atom, resulting in a polar molecule with the capacity to form hydrogen bonds between molecules. These bonds are exceptionally strong dipole-dipole interactions that significantly increase the boiling point compared to substances like H₂S, where lighter hydrogen bonds or primarily London dispersion forces are present. To break these strong interactions and cause H₂O to boil, a high amount of energy is required, which is why its boiling point is unexpectedly high at 100°C. For H₂S, where such bonding is absent, the boiling point is much lower at -60°C.