GC Question

[NguyenDDS]

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Please state whether this is true or false, and why?

"All molecules of an ideal gas have the same kinetic energy at constant temperature."

I'm not understanding the solution in the back of the book.....
Thanks!!

 

[dantemac]

Please state whether this is true or false, and why?

"All molecules of an ideal gas have the same kinetic energy at constant temperature."

I'm not understanding the solution in the back of the book.....
Thanks!!

False.

KE = 0.5 MV^2

For gasses, although the molecular mass (M) will remain the same, Velocity (V) falls under the Boltzmann curve. That is the fancy way of saying gasses only ever have an average speed. Speed is truly never the same. So neither can kinetic energy.

 

[Juggernauts]

The description of the kinetic molecular theory of gases says
"average kinetic energy is proportional to the absolute temp. at the same temperature, all gas molecules have the same average kinetic energy, even if there is more than one type of gas molecule in the container."

I would say the answer is true.

 

[NguyenDDS]

The description of the kinetic molecular theory of gases says
"average kinetic energy is proportional to the absolute temp. at the same temperature, all gas molecules have the same average kinetic energy, even if there is more than one type of gas molecule in the container."

I would say the answer is true.

This is what I thought also.

But the answer is false.

dantemac's answer and explanation was similar to the book's solution. But I still don't understand it..... it coincides with the Kinetic Molecular Theory 😕

 

[Juggernauts]

Maybe the distinction is "average". Meaning the kinetic energy is totaled and them divided by the number of gas molecules. So in theory, maybe the average kinetic energy is the same for all gas molecules, but the individual gas molecules do in fact have there own kinetic energy. Just guessing here.

 

[yappy]

+1. There was a question like this in gen chem exam crackers and it was false. This was because temp was a measurement of average KE.

Maybe the distinction is "average". Meaning the kinetic energy is totaled and them divided by the number of gas molecules. So in theory, maybe the average kinetic energy is the same for all gas molecules, but the individual gas molecules do in fact have there own kinetic energy. Just guessing here.

 

[NguyenDDS]

Maybe the distinction is "average". Meaning the kinetic energy is totaled and them divided by the number of gas molecules. So in theory, maybe the average kinetic energy is the same for all gas molecules, but the individual gas molecules do in fact have there own kinetic energy. Just guessing here.

Awesome! 👍 That makes more sense now, thanks! 🙂

 

[invictusx]

Maybe the distinction is "average". Meaning the kinetic energy is totaled and them divided by the number of gas molecules. So in theory, maybe the average kinetic energy is the same for all gas molecules, but the individual gas molecules do in fact have there own kinetic energy. Just guessing here.

Juggernauts is completely right. The distinction IS average.

 

[NewBee12]

for ideal gases we talk about Average kinetic energy and average speed.
In my physics class I learned that :

KE = (1/2)KT where K is a constant and T is the temperature. So the individual kinetic energies for molecules are not the same but to certain extent the average kinetic energies are the same.

please correct me if i'm wrong