Which of the following substances is predicted to have the lowest boiling point?

• A. NH3 (ammonia)
• B. Ne (neon)
• C. H2O (water)
• D. CH3OH (methanol)

Answer: (B)

Verified step by step guidance

1. Step 1: Understand that boiling point depends on the strength of intermolecular forces present in the substance. Stronger intermolecular forces lead to higher boiling points because more energy is required to separate the molecules.
2. Step 2: Identify the types of intermolecular forces in each substance: NH3, H2O, and CH3OH all exhibit hydrogen bonding, which is a strong type of dipole-dipole interaction. Ne (neon), being a noble gas, only exhibits weak London dispersion forces.
3. Step 3: Compare the strength of intermolecular forces: Hydrogen bonding (in NH3, H2O, CH3OH) is much stronger than London dispersion forces (in Ne). Among the hydrogen-bonding substances, H2O generally has the strongest hydrogen bonds due to its two hydrogen atoms bonded to oxygen, followed by CH3OH and NH3.
4. Step 4: Since Ne only has weak London dispersion forces, it requires the least energy to vaporize, resulting in the lowest boiling point among the given substances.
5. Step 5: Conclude that Ne (neon) has the lowest boiling point because it lacks hydrogen bonding and only has weak dispersion forces, unlike the other substances which have stronger intermolecular attractions.