Which of the following molecules is expected to have the largest dispersion (London) forces?

• A. CH4
• B. NH3
• C. CCl4
• D. CO2

Answer: (C)

Verified step by step guidance

1. Understand that dispersion (London) forces are a type of intermolecular force that arise due to temporary fluctuations in electron density, creating instantaneous dipoles. These forces generally increase with the size and polarizability of the molecule.
2. Compare the molecular sizes and molar masses of the given molecules: CH4 (methane), NH3 (ammonia), CCl4 (carbon tetrachloride), and CO2 (carbon dioxide). Larger molecules with more electrons tend to have stronger dispersion forces.
3. Recognize that CCl4 has the largest molar mass and the most electrons among the options, which means it is more polarizable and will exhibit stronger dispersion forces compared to the others.
4. Note that although NH3 has hydrogen bonding (a stronger intermolecular force), the question specifically asks about dispersion forces, so we focus on molecular size and electron cloud polarizability.
5. Conclude that CCl4, being the largest and most polarizable molecule, will have the largest dispersion (London) forces among the given molecules.