Gen chem question

[flin5845]

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This is from DAT Destroyer 2010 # 38.

Which is a false statement?
A. Kr has lower average speed than Ne at same temo
B. Molecules of gas undergo collisions with each other and the walls of a container
C. Deviations from ideal gas law are greater at low temp and high pressure
D. All molecules of ideal gas have the same kinetic energy at constant temps
E. All of the above are true.

My Answer: E
Correct answer: D

My thinking.
A-true. since Kr is heavier and all molecules have the same kinetic energy at same temp and KE=1/2mv^2 the heavier you are the slower
B. True
C. Ideal gasses work best at high temp, and low pressure so if you deviate it you will go away from ideal gases. statement is true.
D. HOW IS THIS FALSE. From my reasoning on A, I thought that all gasses have the same Kinetic Energy at a constant temp??

 

[mh0000]

Look at a gas velocity distribution curve and you will see that there is a spread of velocities (and thus KE) amongst a collection of gas molecules. What is true (and what you may have been thinking) is that for a given temperature, all ideal gases have the same AVERAGE kinetic energy. But on a molecule to molecule basis, there is a distribution of speeds and KE.

 

[JohnnnyD]

Look at a gas velocity distribution curve and you will see that there is a spread of velocities (and thus KE) amongst a collection of gas molecules. What is true (and what you may have been thinking) is that for a given temperature, all ideal gases have the same AVERAGE kinetic energy. But on a molecule to molecule basis, there is a distribution of speeds and KE.

👍 they have the same AVG KE, not KE