For uranium to be useful as a nuclear fuel, the relative amount of 235U to 238U must be increased from about 0.7% 235U in naturally occurring uranium to about 3%. The process of gas diffusion enrichment utilizes the velocity differences between 238UF6 and 235UF6 to accomplish the desired enrichment. Since the mass differences between 238UF6 and 235UF6 are relatively small, several steps are required in the diffusion process to enrich a natural uranium sample to the desired 3% 235U.
a. Which molecule, 238UF6 or 235UF6, has the greater average velocity at a certain temperature? Explain.
b. In theory, how many steps are required to enrich a uranium sample from 0.700% 235U to 3.00% 235U using the UF6 multistage diffusion process? The molar masses of 23SUF6 and 238UF6 are 349.03 g/mol and 352.05 g/mol, respectively.
c. A certain sample of uranium is reacted w’ith fluorine to form a mixture of 235UF6;(g) and 238UF6(g). After 100 diffusion steps, the gas contains 1526 235UF6 molecules per 1.000 X 10s total number of molecules in the gas. What is the ratio of 235U to 238U atoms in the original sample of uranium?