Question in Relation to Ideal Gas Law and Kinetic Energies

[Strag]

Just need help understanding the concept.

Is it possible for different gases to have the same kinetic energy at the same temperature? I have these listed in my Chad Video notes but I recall a Destroyer GC problem saying that different gases cannot have the same kinetic energy at the same temp...I though Orgoman was referring to average kinetic energy so I didn't pay it much attention.

I know that in any case, different gases exhibit different velocities due to different masses, I'm just wondering if there's a difference between kinetic energies and average kinetic energies?

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[yappy]

I'm pretty sure that gases will have the same average KE at the same temp.

As you stated the velocity and mass will be related by the equation KE=1/2mv^2.

Just need help understanding the concept.

Is it possible for different gases to have the same kinetic energy at the same temperature? I have these listed in my Chad Video notes but I recall a Destroyer GC problem saying that different gases cannot have the same kinetic energy at the same temp...I though Orgoman was referring to average kinetic energy so I didn't pay it much attention.

I know that in any case, different gases exhibit different velocities due to different masses, I'm just wondering if there's a difference between kinetic energies and average kinetic energies?

 

[bharat008]

Just need help understanding the concept.

Is it possible for different gases to have the same kinetic energy at the same temperature? I have these listed in my Chad Video notes but I recall a Destroyer GC problem saying that different gases cannot have the same kinetic energy at the same temp...I though Orgoman was referring to average kinetic energy so I didn't pay it much attention.

I know that in any case, different gases exhibit different velocities due to different masses, I'm just wondering if there's a difference between kinetic energies and average kinetic energies?

All the gases have the same AVERAGE KINETIC ENERGY..
You can't say all the gases have same kinetic energy b/c they don't. You assume that their AVERAGE KE is same at same temp..

 

[Strag]

Ok that's what I thought. I'm very confused on #43 for Dat Destroyer GC. He says that it's false that all molecules of an ideal gas have the same kinetic energy at constant temperature. In the back of the solutions he mentioned D is wrong but describes the answer in terms of speed (speeds are not the same).

Is choice D supposed to read "All molecules of an ideal gas have the same speed at constant temperature" so that it would be right (meaning it would be the answer in which of the following is false type of questions).

 

[bharat008]

Ok that's what I thought. I'm very confused on #43 for Dat Destroyer GC. He says that it's false that all molecules of an ideal gas have the same kinetic energy at constant temperature. In the back of the solutions he mentioned D is wrong but describes the answer in terms of speed (speeds are not the same).

Is choice D supposed to read "All molecules of an ideal gas have the same speed at constant temperature" so that it would be right (meaning it would be the answer in which of the following is false type of questions).

If it mentions that all the gases has same KINETIC ENERGY at same Temp. = WRONG = They have same AVERAGE KE at same TEmp

If they mention all gases have same speed at same temp = WRONG = depends on their mass = the lower the mass the higher the speed..

👍

 

[Strag]

Researched my own question.

http://www.***********.com/showthre...e-have-the-same-kinetic-energy.-Or-don-t-they

In a destroyer problem I was trying to solve (which of the following is false), the following statement was false: "All molecules of an ideal gas have the same kinetic energy at constant temperature". I remember Chad saying specifically (because I wrote in on a "important to know" sticky) that kinetic energy is proportional to temperature so if temperature is constant then so is kinetic energy. However, velocity depends on mass.

I though maybe the statement was false because "all" is usually too strict and can be accounted as false BUT In the destroyer answer explanation, they refer to the Boltzmann distribution as the explanation for why the above statement is false. I don't really understand this at all. Is kinetic energy proportional to temperature?

Please help!!​

chad:

I've seen this question a couple times now and actually made sure to emphasize this the last time I presented this material recently. The key here is that the average kinetic energy of two different samples of gas will be the same if the two samples are at the same temperature. But the molecules in either sample will have a distribution of speeds and therefore a distribution of kinetic energies (some molecules will be moving faster and some slower). So the average kinetic energy between two different samples is the same but the individual molecules in the samples will not each have the same exact kinetic energy.

Hope this helps to clarify.​

 

[Strag]

If it mentions that all the gases has same KINETIC ENERGY at same Temp. = WRONG = They have same AVERAGE KE at same TEmp

If they mention all gases have same speed at same temp = WRONG = depends on their mass = the lower the mass the higher the speed..

👍

Thanks! Makes sense now.

 

[bharat008]

Thanks! Makes sense now.