Calculating the Average Kinetic Energy of a Helium Atom at 20°C

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SUMMARY

The average kinetic energy of a helium atom at 20°C is calculated using the equation E = kT/2, where k is the Boltzmann constant. The correct average kinetic energy is 4.0 x 10^-21 joules, derived from the simplified calculation of kT. The initial attempt incorrectly applied the degrees of freedom, resulting in a value of 6.1 x 10^-21 joules. Understanding the distinction between total kinetic energy and average kinetic energy per degree of freedom is crucial for accurate calculations.

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  • Understanding of the Boltzmann constant (k)
  • Familiarity with the concept of degrees of freedom in kinetic theory
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Homework Statement



What is the average kinetic energy of an atom of helium gas at a temperature of 20 degrees C?


Homework Equations



N/A

The Attempt at a Solution



Here's my attempt at a solution: Using the equation E = kT/2 for each degree of freedom, I found that KE = 3kT/2 since an atom of He has three degrees of freedom in translational KE. Using this logic I fould that KE = 6.1 x 10^-21 while the correct answer should be 4.0 x 10^-21. Can someone help me understand where my logic/reasoning is incorrect? Thanks.
 
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Looks okay to me. Someone got the 4.0 answer by just finding kT.
 
That's what I thought my teacher might have done. Thanks!
 

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