Which of the following substances exhibits dipole-dipole intermolecular forces in its pure form?

• A. O2
• B. CH4
• C. HCl
• D. CO2

Answer: (C)

Verified step by step guidance

1. Identify the type of molecules given: O2, CH4, HCl, and CO2. Determine whether each molecule is polar or nonpolar based on its molecular geometry and the electronegativity difference between atoms.
2. Recall that dipole-dipole intermolecular forces occur between polar molecules, which have a permanent dipole moment due to uneven charge distribution.
3. Analyze O2: It is a diatomic molecule with two identical oxygen atoms, so the electronegativity difference is zero, making it nonpolar and only exhibiting London dispersion forces.
4. Analyze CH4: Methane has a tetrahedral geometry with four identical C-H bonds symmetrically arranged, resulting in a nonpolar molecule with only London dispersion forces.
5. Analyze HCl: Hydrogen chloride is a diatomic molecule with a significant electronegativity difference between H and Cl, making it polar and capable of dipole-dipole interactions in its pure form.