A process called gaseous diffusion is often used to separate isotopes of uranium

Question

A process called gaseous diffusion is often used to separate isotopes of uranium-that is, atoms of the elements that have different masses, such as 235U and 238U. The only gaseous compound of uranium at ordinary temperatures is uranium hexafluoride, UF6. Speculate on how 235UF6 and 238UF6 molecules might be separated by diffusion.

The molar masses for 235UF6 and 238UF6 molecules are 0.349 kg/mol and 0.352 kg/mol, respectively. If uranium hexafluoride acts as an ideal gas, what is the ratio of the root-mean-square speed of 235UF6 molecules to that of 238UF6molecules if the temperature is uniform?

Explanation / Answer

ration of RMS,

v1/v2 = sqrt( M2/M1)

so,

v(235U)/v(238U) = sqrt ( M( 238U)/M(235U))
so,
v(235U)/v(238U) =sqrt( 0.352/0.349)
solving it,
the ratio of the root-mean-square speed of 235UF6 molecules to that of 238UF6molecules ,

v(235U)/v(238U)=1.004289 ~1.0043

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