Rank the following molecules in order of increasing melting point (lowest mp to highest mp).

• A. II < I < III
• B. III < I < II
• C. II < III < I
• D. III < II < I

Answer: (A)

Verified step by step guidance

1. Identify the functional groups present in each molecule. Molecule I is a ketone, Molecule II is an alkane, and Molecule III is a carboxylic acid.
2. Understand the impact of functional groups on melting points. Carboxylic acids (Molecule III) can form hydrogen bonds, which significantly increase melting points. Ketones (Molecule I) have dipole-dipole interactions, while alkanes (Molecule II) only have van der Waals forces.
3. Consider the molecular weight and structure. All molecules have similar carbon chain lengths, so the functional group interactions will be the primary factor affecting melting points.
4. Rank the molecules based on the strength of intermolecular forces. Molecule III, with hydrogen bonding, will have the highest melting point. Molecule I, with dipole-dipole interactions, will have a higher melting point than Molecule II, which only has van der Waals forces.
5. Conclude the ranking order based on the analysis: II < I < III.