Given the following molecules: CHCl3, CH4, and CH3F, which option correctly ranks them from strongest to weakest dipole-dipole forces?

• A. CH4 > CH3F > CHCl3
• B. CH4 > CHCl3 > CH3F
• C. CHCl3 > CH3F > CH4
• D. CH3F > CHCl3 > CH4

Answer: (D)

Verified step by step guidance

1. Step 1: Understand that dipole-dipole forces arise from the polarity of molecules, which depends on the difference in electronegativity between atoms and the molecular geometry.
2. Step 2: Analyze each molecule's polarity by considering the electronegativity of the atoms attached to carbon and the symmetry of the molecule. For example, CH4 is nonpolar because all four hydrogens are identical and symmetrically arranged.
3. Step 3: Evaluate CH3F, where fluorine is highly electronegative, creating a strong dipole moment due to the C-F bond, making the molecule polar with significant dipole-dipole interactions.
4. Step 4: Consider CHCl3, which has three chlorine atoms bonded to carbon. Chlorine is less electronegative than fluorine but more than hydrogen, so CHCl3 is polar but generally less so than CH3F.
5. Step 5: Rank the molecules based on their polarity and resulting dipole-dipole forces: the molecule with the strongest dipole moment (CH3F) has the strongest dipole-dipole forces, followed by CHCl3, and finally CH4 with the weakest (essentially none).