What gas would be expected to have the lowest rate of effusion?

The rate of effusion of a gas is inversely related to its molar mass, according to Graham's law of effusion. Therefore, a heavier gas, such as xenon (Xe) or carbon dioxide (CO₂), would have a lower rate of effusion compared to lighter gases like helium or hydrogen. Among common gases, xenon, with a high molar mass of approximately 131.3 g/mol, would be expected to have one of the lowest rates of effusion.