Question

Natural uranium is a mixture of ²³⁸U (99.3%, monisotopic mass = 238.05 amu) and ²³⁵U (0.7%, monisotopic mass = 235.04 amu). The 235U isotope is essential to nuclear reactors. We isolate this isotope by converting a sample that contains both forms of uranium to UF₆. What is the molecular mass of the UF₆ compound if only ²³⁸U is used? What is the molecular mass of the UF₆ compound if only ²³⁵U is used? What would the (rate of ²³⁵U)/(rate of ²³⁸U) be according to Graham’s law?How much faster will the 235 isotope travel compared to the 238 isotope?? Show work please. I have tried many times but keeps saying my answers are incorrect.

Answer 1

atomic mass of U²³⁸ = 238.05 g

MOLECUALR MASS OF UF₆ CONTAINING  U²³⁸ = 238.05 + 6 X 18.99 = 351.99 g

MOLECUALR MASS OF UF₆ CONTAINING  U²³⁵ = 235.04 + 6 X 18.99 = 348.98 g

RATE OF DIFFUSION IS INVERSELY PROPORIONAL TO SUARE ROOT OF MOLAR MASS.

  (rate of 235U)/(rate of 238U) = [(MW of 238U)/(W of 235U)]^1/2

= [351.99/348.98]^1/2

= 1.004

ALMOST BOTH ISOTOPES TRAVEL WITH SAME SPEED.

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FOR VALUABLE INFORMATION 1 amu = 1.67377 x 10 ^-24 gram

to remember, 1 amu x avagadro number = 1

so that atomic masse or molar masses can be expressed in grams

for instance mola mass of U238 = 238.05 X 1.67377 x 10 ^-24 gram X 6.02 X 10²³

= 238.05 X 1

= 238.05 g

HOPE CATCH IT.