There are two important isotopes of uranium— and ; these isotopes are nearly identical chemically but have different atomic masses. Only is very useful in nuclear reactors. One of the techniques for separating them (gas diffusion) is based on the different average velocities of uranium hexafluoride gas, . (a) The molecular masses for and are 349.0 g/mol and 352.0 g/mol, respectively. What is the ratio of their average velocities?