The table below lists experimental data for four molecular substances that all contain only carbon, hydrogen, and chlorine.
Substance | Molar mass (g·mol⁻¹) | Dipole moment (D)
A | 99 | 0.0
B | 99 | 1.4
C | 133 | 0.0
D | 133 | 1.8
All four substances are liquids at 25 °C.
Use the information provided to analyze the relative magnitudes of intermolecular forces among the liquids.
(a) Rank the four substances from lowest to highest normal boiling point. Justify your ranking with quantitative or qualitative reasoning that references both dispersion and dipole–dipole interactions as appropriate.
(b) Substance D and substance B both possess non-zero dipole moments. Explain why the difference in their dipole moments alone is insufficient to account for the full difference you predicted in part (a).
(c) A mixture is prepared that contains equal numbers of molecules of substances A and B. Describe the two most significant types of intermolecular interactions that exist in the liquid mixture and comment on how each interaction influences the overall volatility of the mixture compared with the pure components.