Kinetic Energy of Ideal Gases and Temp??

[Krentist_72]

Hi all, feeling like I'm either getting conflicting information or am missing some piece of crucial info to fully get this concept.

So in DAT Destroyer GC (2016), questions 44, 68, and 70 discuss temperature and Kinetic Energy.

68's answer says "all molecules of an ideal gas have the same kinetic energy at a constant temperature" is FALSE and gives Boltzmann's curve to prove that at a given temp, molecules move at different speeds.

However, 44 has a scenario where Cl2, Ar, NH3, CH4, and N2 are all together at constant pressure, temperature, and volume. The answer says "Since the temperature is the same, the molecules all have the same average kinetic energy."
Basically 44 says that at constant temp, molecules have the same avg KE and 68 says that the molecules at a constant temperature DO NOT have the same KE.

I tried to solve this myself with this link (http://chemwiki.ucdavis.edu/Core/Ph...netic_Theory_of_Gases/Kinetic_Theory_of_Gases) which says "The average kinetic energy of a gas particle is directly proportional to the temperature. An increase in temperature increases the speed in which the gas molecules move. All gases at a given temperature have the same average kinetic energy"

So is 68 wrong? Do all gases at the same temperature have the same KE? Or am I missing some keyword/concept that can help make this click?

---

Members don't see this ad.

 

[DAT Destroyer]

Hi all, feeling like I'm either getting conflicting information or am missing some piece of crucial info to fully get this concept.

So in DAT Destroyer GC (2016), questions 44, 68, and 70 discuss temperature and Kinetic Energy.

68's answer says "all molecules of an ideal gas have the same kinetic energy at a constant temperature" is FALSE and gives Boltzmann's curve to prove that at a given temp, molecules move at different speeds.

However, 44 has a scenario where Cl2, Ar, NH3, CH4, and N2 are all together at constant pressure, temperature, and volume. The answer says "Since the temperature is the same, the molecules all have the same average kinetic energy."
Basically 44 says that at constant temp, molecules have the same avg KE and 68 says that the molecules at a constant temperature DO NOT have the same KE.

I tried to solve this myself with this link (http://chemwiki.ucdavis.edu/Core/Ph...netic_Theory_of_Gases/Kinetic_Theory_of_Gases) which says "The average kinetic energy of a gas particle is directly proportional to the temperature. An increase in temperature increases the speed in which the gas molecules move. All gases at a given temperature have the same average kinetic energy"

So is 68 wrong? Do all gases at the same temperature have the same KE? Or am I missing some keyword/concept that can help make this click?

Don't confuse AVERAGE Kinetic Energy with Kinetic Energy. Think of it as a group of kids.....I will use my Summer 2016 DAT group as an example. If 1 is the lowest.....and 10 is the highest..,.,,,,,,I give the group AVERAGE a 7.......in terms of energy and work ethic. Now..... This is only an average......some kids are work horses.....I give them a 10...others are a 1.....they are sleepy all the time. Molecules at a given temperature do NOT all have the same kinetic energy.....some are colliding with each other, some are hitting the container walls,,,,,some are not,,,,,,BUT I can say that at a GIVEN TEMPERATURE......we have an average kinetic energy. The key word is AVERAGE !!!!

I hope this helps.

Dr. Romano

 

[Krentist_72]

Molecules at a given temperature do NOT all have the same kinetic energy.....some are colliding with each other, some are hitting the container walls,,,,,some are not,,,,,,BUT I can say that at a GIVEN TEMPERATURE......we have an average kinetic energy. The key word is AVERAGE !!!!

Ohhh ok of course... So they all have the same AVG KE, because all of them are creating the average together. But if we broke down the average gas by gas, each individual gas would have a different KE even though theyre at the same temperature?
Thanks for your response!!