Enriched uranium is produced via gaseous diffusion of UF6. Suppose a process were developed to allow diffusion of gaseous uranium atoms, U (g). Calculate the ratio of diffusion rates of U235 and U238, and compare it to the ratio for UF6 given in the essay.

Answer 1

What essay are you talking about?

The diffusion constant D, which is proportional to the diffusion rate, is proportional to sqrt(1/M), where M is the molecular or atomic weight.

You are probably supposed to compare sqrt(238/235) with sqrt(352/349).
The former applies to the atomic vapor and the latter applies to the hexafluoride.