Which of the following substances has the highest boiling point?

• A. O_2
• B. CH_4
• C. CO_2
• D. H_2O

Answer: (D)

Verified step by step guidance

1. Identify the types of intermolecular forces present in each substance: O_2, CH_4, CO_2, and H_2O. These forces largely determine boiling points.
2. Recall that O_2 and CO_2 are nonpolar molecules, so their intermolecular forces are primarily London dispersion forces, which are relatively weak.
3. Recognize that CH_4 is also nonpolar and experiences London dispersion forces, but its molecular size and shape affect the strength of these forces compared to O_2 and CO_2.
4. Understand that H_2O is a polar molecule capable of hydrogen bonding, a much stronger intermolecular force than dispersion forces.
5. Conclude that because hydrogen bonding is stronger than dispersion forces, H_2O has the highest boiling point among the given substances.