Final answer:
LiCl would have the highest boiling point due to its strong ionic bonds that require more energy to break compared to the intermolecular forces in the other listed substances.
Step-by-step explanation:
To determine which of the given substances would have the highest boiling point, we need to consider the types of intermolecular forces each substance can exhibit since these forces directly affect boiling points. Kr (Krypton) is a noble gas with weak London dispersion forces. HCl (Hydrochloric acid) is a polar molecule and displays dipole-dipole interactions. Cl2 (Chlorine) is a diatomic molecule with London dispersion forces. CH4 (Methane) is a nonpolar molecule, also with London dispersion forces but with low molecular weight. Lastly, LiCl (Lithium chloride) is an ionic compound that exhibits strong ionic bonds.
Amongst these, LiCl would have the highest boiling point due to the strong electrostatic attractions between ions, which require a lot of energy to overcome. Following this reasoning, we can arrange the substances from lowest to highest boiling points as follows: Kr < CH4 < Cl2 < HCl < LiCl.