Arrange the following compounds in order of increasing boiling point: CH4, NH3, H2O, CO2.

• A. CH4 < CO2 < NH3 < H2O
• B. NH3 < CH4 < CO2 < H2O
• C. CO2 < CH4 < NH3 < H2O
• D. CH4 < NH3 < CO2 < H2O

Answer: (A)

Verified step by step guidance

1. Identify the types of intermolecular forces present in each compound: CH4 (methane) has London dispersion forces, CO2 (carbon dioxide) has London dispersion forces but is linear and nonpolar, NH3 (ammonia) has hydrogen bonding due to N-H bonds, and H2O (water) has strong hydrogen bonding due to O-H bonds.
2. Recall that boiling point generally increases with the strength of intermolecular forces: hydrogen bonding > dipole-dipole interactions > London dispersion forces.
3. Compare CH4 and CO2: both have London dispersion forces, but CO2 is larger and more polarizable, so CO2 typically has a higher boiling point than CH4.
4. Compare NH3 and H2O: both exhibit hydrogen bonding, but H2O has stronger hydrogen bonding because oxygen is more electronegative than nitrogen and water molecules can form more hydrogen bonds per molecule.
5. Arrange the compounds in order of increasing boiling point based on the strength of their intermolecular forces: CH4 < CO2 < NH3 < H2O.