Predicting the exact boiling point of a substance based solely on its molar mass and the presence of London dispersion forces is not possible without more information. However, we can provide a general idea of how these factors might influence the boiling point.London dispersion forces are the weakest of the van der Waals forces, and they arise due to the temporary fluctuations in electron distribution around molecules. These forces generally increase with increasing molar mass, as larger molecules have more electrons and a larger surface area for contact between molecules.A substance with a molar mass of 120 g/mol and predominantly London dispersion forces would likely have a higher boiling point than a similar substance with a lower molar mass. This is because the larger molar mass would lead to stronger London dispersion forces, which would require more energy to overcome when transitioning from the liquid to the gas phase.However, without more information about the specific substance, its structure, and any other intermolecular forces that may be present, it is not possible to provide an exact boiling point prediction.