Which of the following compounds exhibits only dispersion and dipole-dipole intermolecular interactions?
1) Na
2) HCl
3) BH3
4) CH3NHC4H9
To determine which compound exhibits only dispersion and dipole-dipole intermolecular interactions, we need to analyze the nature of intermolecular forces in each compound.
1) Na (sodium) is an elemental metal and does not exhibit dispersion or dipole-dipole interactions. Instead, it forms metallic bonds due to the delocalization of its valence electrons.
2) HCl (hydrochloric acid) is a polar covalent compound, with a hydrogen atom bonded to a chlorine atom. HCl exhibits both dispersion forces and dipole-dipole interactions due to the partial positive charge on hydrogen and the partial negative charge on chlorine. Therefore, it can have both types of intermolecular interactions.
3) BH3 (boron trihydride) is a nonpolar compound because it has a trigonal planar molecular geometry with the boron atom in the center and three hydrogen atoms surrounding it. Since it lacks a permanent dipole moment, BH3 exhibits only dispersion forces.
4) CH3NHC4H9 (a tertiary amine) has a polar nature due to the presence of both polar bonds and a lone pair of electrons on the nitrogen atom. Thus, it exhibits both dispersion forces and dipole-dipole interactions.
From the given compounds, BH3 (boron trihydride) exhibits only dispersion forces and does not have dipole-dipole interactions. Therefore, BH3 is the correct answer to the question.