A gas cylinder contains a mixture of carbon dioxide and oxygen, which have different molecular masses. The contents of the cylinder are in thermal equilibrium. Which of the following statements is correct?

Question

Question 1 options:
A) All carbon dioxide molecules and all oxygen molecules travel at the same speed.

B) The root mean square (RMS) speed of the carbon dioxide molecules is equal to the root mean square (RMS) speed of the oxygen molecules.

C) The average kinetic energy of the carbon dioxide molecules is equal to the average kinetic energy of the oxygen molecules.

D) Because they have a smaller mass, all oxygen molecules are traveling faster at any instant than all carbon dioxide molecules.

Answer 1

(C) is the correct answer.

The average (and rms) speed of the O2 molecules is faster, but that does not mean that all the O2 molecules are faster than all of the CO2 molecules. Their Maxwell-Boltzmann velocity distributions are shifted from one another, but overlap.