Temperature required for new rms speed

AI Thread Summary
To find the temperature at which helium gas molecules have an rms speed of 733 m/s, the equation Vrms = √(3kT/m) is used. The attempt at the solution incorrectly calculates T, resulting in an unreasonably high value of 5.187e25 K. The mass 'm' should be the mass of a single helium molecule, which is approximately 0.004 kg, not the mass of a mole. Clarification is provided that the ideal gas law (PV = nRT) requires the number of moles 'n' for temperature calculations, which is not given in the problem. Accurate temperature calculation hinges on using the correct molecular mass and understanding the context of the ideal gas law.
rubenhero
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Homework Statement


c) Find T, the temperature at which He gas molecules have an rms speed of v = 733 m/s.


Homework Equations


Vrms = √(3kT/m)


The Attempt at a Solution


(Vrms2m)/3k = T
(7332*.004kg)/(3*1.381e-23J/k) = T
5.187e25k = T

Any help with figuring out what I did wrong is appreciated!
 
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Is not 'm' the mass of one MOELECULE of hydrogen?
 
You could use the following to solve if you are given the quantity of material (n):

P*V=n*R*T <=> T=(P*V)/(n*R)

For R is a constant: R=8.31
 
Thank you grzz and mtayab1994 for responding. It would be easier if the problem did provide n to use PV = nRT. I am confused, should I be using .008 kg for the mass because helium gas has 2 atoms?
 
rubenhero said:
Thank you grzz and mtayab1994 for responding. It would be easier if the problem did provide n to use PV = nRT. I am confused, should I be using .008 kg for the mass because helium gas has 2 atoms?

no you are fine with using .004kg
 
Last edited:
By the way you can use the following as well
ee2357aaf50f4db86dac6622e7f8cc02.png
 

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