When oil and vinegar are mixed together, they quickly separate into two layers. Which type of intermolecular force is primarily responsible for this behavior?

• A. Dipole-dipole interactions between oil and vinegar molecules
• B. Hydrogen bonding between oil and vinegar molecules
• C. London dispersion forces between oil and vinegar molecules
• D. Strong hydrogen bonding among vinegar molecules and weak London dispersion forces among oil molecules prevent mixing

Answer: (D)

Verified step by step guidance

1. Identify the nature of the two substances: vinegar is mostly water and acetic acid, which are polar and capable of hydrogen bonding; oil is nonpolar and primarily exhibits London dispersion forces.
2. Understand that like dissolves like: polar substances tend to mix with other polar substances due to strong intermolecular forces like hydrogen bonding, while nonpolar substances mix with nonpolar substances due to London dispersion forces.
3. Recognize that the strong hydrogen bonding among vinegar molecules creates a cohesive network that does not interact favorably with the nonpolar oil molecules.
4. Note that oil molecules experience only weak London dispersion forces and do not form strong interactions with the polar vinegar molecules.
5. Conclude that the difference in intermolecular forces—strong hydrogen bonding in vinegar versus weak London dispersion forces in oil—causes the two liquids to separate into layers rather than mix.