Final answer:
The strongest intermolecular force between ethane (CH3CH3) and propylamine (CH3CH2CH2NH2) is hydrogen bonding, mainly occurring within the propylamine solvent molecules.
Step-by-step explanation:
The strongest type of intermolecular force between the solute ethane (CH3CH3) in the gas phase and the solvent propylamine (CH3CH2CH2NH2) in the liquid phase is most likely engaged through hydrogen bonding. In propylamine, the presence of a hydrogen atom bonded to a nitrogen, an electronegative atom, allows it to participate in hydrogen bonding. Ethane, being a nonpolar molecule, primarily exhibits London dispersion forces, which are the weakest type of van der Waals forces.
However, when it is dissolved in propylamine, it is possible for ethane to induce a temporary dipole in the propylamine molecules that leads to a dispersion force interaction. Nonetheless, the dominant and strongest interaction in this solution is between the propylamine molecules themselves, which can form hydrogen bonds with each other.