Temperature required for new rms speed

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SUMMARY

The discussion focuses on calculating the temperature required for helium gas molecules to achieve a root mean square (rms) speed of 733 m/s using the formula Vrms = √(3kT/m). The user initially miscalculated temperature by incorrectly applying the mass of helium. The correct mass of a helium molecule is 0.004 kg. The final calculation for temperature, T, is derived from the equation T = (Vrms² * m) / (3k), yielding T = 5.187e25 K, which indicates a significant error in the calculation process.

PREREQUISITES
  • Understanding of the root mean square speed formula (Vrms = √(3kT/m))
  • Knowledge of the Boltzmann constant (k = 1.381e-23 J/K)
  • Familiarity with the ideal gas law (PV = nRT)
  • Basic concepts of molecular mass, specifically for helium (0.004 kg)
NEXT STEPS
  • Review the derivation of the rms speed formula for different gases
  • Learn about the implications of molecular mass on gas behavior
  • Study the ideal gas law and its applications in thermodynamics
  • Explore the significance of the Boltzmann constant in statistical mechanics
USEFUL FOR

Students studying thermodynamics, physics enthusiasts, and anyone interested in gas behavior and molecular speed calculations.

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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