Which one of the following substances would have the highest heat of vaporization?

• A. CO2
• B. NH3
• C. CH4
• D. H2O

Answer: (D)

Verified step by step guidance

1. Understand that the heat of vaporization is the amount of energy required to convert a substance from liquid to gas at its boiling point, overcoming intermolecular forces.
2. Identify the types of intermolecular forces present in each substance: CO2 (nonpolar, London dispersion forces), NH3 (polar, hydrogen bonding), CH4 (nonpolar, London dispersion forces), and H2O (polar, strong hydrogen bonding).
3. Recognize that stronger intermolecular forces require more energy to break, leading to a higher heat of vaporization.
4. Compare the strength of intermolecular forces: H2O has the strongest hydrogen bonding among the listed substances, NH3 has hydrogen bonding but weaker than H2O, and CO2 and CH4 have weaker London dispersion forces.
5. Conclude that because H2O has the strongest intermolecular forces, it will have the highest heat of vaporization.