A mixture of 8.0 mol Ne and 8.0 mol Xe are at STP in a rigid container. Which of the following statements is TRUE?
A) Both gases have the same average kinetic energy.
B) Both gases contribute equally to the density of the mixture under these conditions.
C) Both gases have the same molecular speed.
D) The mixture has a volume of 22.4 L
E) All of the above are TRUE.

A) and B)  

Explanation:

Let's examine each of the statements in turn.

A) Average kinetic energy

TRUE

A postulate of the Kinetic Molecular Theory is that the molecules of a gas have the same average kinetic energy at the same temperature.

B) Contribution to density

TRUE

There is an equal number of moles, so there are equal numbers of molecules of each gas. The gases will contribute equally to the density.

C) Molecular  speeds

FALSE.

The molecules of each gas have the same average kinetic energy.

KE = ½mv²

The less massive neon molecules must move faster to have the same kinetic energy as the xenon molecules.

D) Volume

FALSE

The volume is that of the rigid container. It will be 22.4 L only if that is the volume of the container.