Rank the following compounds in order of increasing strength of intermolecular forces: C2H6, H2O, CH3Cl, CO2.

• A. C2H6 < CO2 < CH3Cl < H2O
• B. CO2 < C2H6 < H2O < CH3Cl
• C. CH3Cl < CO2 < C2H6 < H2O
• D. H2O < CH3Cl < CO2 < C2H6

Answer: (A)

Verified step by step guidance

1. Identify the types of intermolecular forces present in each compound: C2H6 (ethane), H2O (water), CH3Cl (chloromethane), and CO2 (carbon dioxide). The main types to consider are London dispersion forces, dipole-dipole interactions, and hydrogen bonding.
2. Determine the polarity of each molecule: C2H6 and CO2 are nonpolar, so they primarily exhibit London dispersion forces. CH3Cl is polar and exhibits dipole-dipole interactions in addition to London forces. H2O is highly polar and can form hydrogen bonds, which are stronger than dipole-dipole interactions.
3. Consider molecular size and shape: Larger molecules with more electrons generally have stronger London dispersion forces. Compare the molecular weights and structures of C2H6 and CO2 to assess their relative dispersion forces.
4. Rank the compounds based on the strength of their intermolecular forces: start with the weakest (nonpolar molecules with only dispersion forces) and move to stronger forces (dipole-dipole and hydrogen bonding).
5. Combine your analysis to order the compounds from weakest to strongest intermolecular forces: C2H6 < CO2 < CH3Cl < H2O, because ethane has the weakest forces, carbon dioxide has slightly stronger dispersion forces, chloromethane has dipole-dipole interactions, and water has the strongest hydrogen bonding.