Root-mean-square velocity

  • Thread starter mit_hacker
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  • #1
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Homework Statement



(Q) Hydrogen molecules have a mass of 2u and oxygen molecules have a mass of 32u, where u is defined as an atomic mass unit (u = 1.660540 \times 10^{-27}\; {\rm kg}). Compare a gas of hydrogen molecules to a gas of oxygen molecules.

At what gas temperature T_rms would the root-mean-square (rms) speed of a hydrogen molecule be equal to that of an oxygen molecule in a gas at 300 K?
State your answer numerically, in kelvins, to the nearest integer.

Homework Equations



v = sqrt(3kT/m) where k is Boltzmann's constant.

The Attempt at a Solution



Using the above equation gives that Temperature is 300/16 = 18.75K. I know that this is a crazy answer but please don't laugh:frown:

What's wrong with my solution?
 

Answers and Replies

  • #2
HallsofIvy
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I'll promise not to laugh if you will tell me why 18.75 K is a "crazy answer"!
 
  • #3
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Because.....

Thats almost close to absolute 0 and when i fed the answer in, it said "not quite" which I rake to be a euphemism for "this is nonsense!!!!"
 
  • #4
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the question requests the "the nearest integer" your result is correct, but I think the anwser should be 19
 

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