The two isotopes of uranium, 238U and 235U, can be separated by effusion of the corresponding UF6 gases. What is the ratio (in the form of a decimal) of the root-mean-square speed of 238UF to that of 235UF6 at constant temperature?

Answer 1

u(rms) = sqrt(3RT/M)

Calculate rms for UF6(238) and do the same for UF6(235), take the ratio of 238/235.
Use 8.314 for R.

Answer 2

I got the square root of 238/235 is 1, and I know that R mutiplied by 3 is 24.9, but I'm stuck right there.

Answer 3

Do what DrBob has suggested

Write an expression for the rms for UF6(238) and do the same for UF6(235), take the ratio of (rms) 238/235.

so
rms(238)=sqrt(3RT/238)

rms(235)=sqrt(3RT/235)

ratio=rms(238)/rms(235)
=sqrt(3RT/238)/sqrt(3RT/235)

as 3RT will cancel

ratio= sqrt(1/238)/sqrt(1/235)
=sqrt(1/238)/(1/235)
=sqrt(235/238)

Answer 4

from there how do we right the ratio?