Final answer:
In a gaseous sample of HI, both London dispersion forces and dipole-dipole interactions are present. Hydrogen bonding and ionic forces do not occur in HI as it is not an ionic compound, nor does it have hydrogen bonded to an extremely electronegative atom.
Step-by-step explanation:
The question asks what intermolecular forces can exist in a gaseous sample of HI. The options given are hydrogen bonding, ionic forces, London dispersion forces, and dipole-dipole interactions.
Hydrogen iodide (HI) is a diatomic molecule and does not form hydrogen bonds because hydrogen is not bonded to an electronegative atom like fluorine, oxygen, or nitrogen. Therefore, hydrogen bonding is not a correct answer. HI is not an ionic compound, so ionic forces do not exist within a sample of gaseous HI. However, HI is a polar molecule with a permanent dipole due to the difference in electronegativity between hydrogen and iodine, leading to dipole-dipole interactions. London dispersion forces are also present in all molecules, including HI, and they arise due to the temporary formation of instantaneous dipoles.