Which intermolecular forces are present between two molecules of CH3CF3 (1,1,1-trifluoroethane)?

• A. Hydrogen bonding only
• B. London dispersion forces and dipole-dipole interactions
• C. London dispersion forces only
• D. Hydrogen bonding and dipole-dipole interactions

Answer: (B)

Verified step by step guidance

1. Identify the types of atoms and bonds present in the molecule CH3CF3 (1,1,1-trifluoroethane). Notice that it contains carbon (C), hydrogen (H), and fluorine (F) atoms.
2. Determine if hydrogen bonding is possible. Hydrogen bonding typically occurs when hydrogen is directly bonded to highly electronegative atoms like nitrogen (N), oxygen (O), or fluorine (F). In CH3CF3, hydrogen is bonded to carbon, not directly to fluorine, so hydrogen bonding is not present.
3. Recognize that all molecules exhibit London dispersion forces (also called induced dipole-induced dipole interactions) due to temporary fluctuations in electron density. Therefore, London dispersion forces are present between CH3CF3 molecules.
4. Check for permanent dipoles in the molecule. Since fluorine is highly electronegative, the C–F bonds are polar, creating a molecular dipole moment. This means dipole-dipole interactions are also present between CH3CF3 molecules.
5. Conclude that the intermolecular forces present between two CH3CF3 molecules are London dispersion forces and dipole-dipole interactions, but not hydrogen bonding.