Which intermolecular forces are present in pure samples of both CH4 and CF4?

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

Answer: (C)

Verified step by step guidance

1. Identify the molecular structure and polarity of CH4 (methane). CH4 is a tetrahedral molecule with four identical C-H bonds, which are nonpolar, making the overall molecule nonpolar.
2. Identify the molecular structure and polarity of CF4 (carbon tetrafluoride). CF4 is also tetrahedral with four identical C-F bonds. Although C-F bonds are polar, the symmetrical arrangement cancels out the dipoles, resulting in a nonpolar molecule.
3. Recall that nonpolar molecules primarily exhibit London dispersion forces, which are weak intermolecular forces caused by temporary fluctuations in electron density.
4. Understand that dipole-dipole interactions require polar molecules with permanent dipoles, which neither CH4 nor CF4 have due to their symmetrical shapes.
5. Recognize that hydrogen bonding requires hydrogen atoms bonded to highly electronegative atoms (N, O, or F), which is not the case for either CH4 or CF4.