All gases at the same temperature have the same kinetic energy; however, this does not necessarily mean the gas molecules move at the same speed. At 25°C, which gas will have move the slowest? Kr (molar mass=83.80 g/mol) He (molar mass = 4.00 g/mol) Ne (molar mass = 20.18 g/mol) Ar (molar mass= 39.95 g/mol)