Question

If all of the gas molecules on the right side of the room move over to the left side of the room. Which statement regarding this event would be true?

A) It would require work.

B) A pressure gradient would be created in the room.

C) The entropy of the gas would decrease

D) All of the above

E) None of the above

Please explain.

Answer 1

When all of the gas molecules on the right side of the room move over to the left side of the room,

It would require work as the gas molecules are displaced from one to another side. Since the molecules possess somewhat mass, work has to be done to move them from one place to another.

A pressure gradient will be created in the room. As the number of molecules per unit volume increases when we move all the molecules to one side. Consequently pressure will be higher and hence a pressure gradient will be created.

From gas equation we have -

PV = nRT

Or P = (n/V)*RT

Where (n/V) is the number of moles of the gas per unit volume which increases with the increase in number of molecules per unit volume.

Entropy of the gas would decrease as more number of molecules have to be adjust in smaller volume when all the molecules move to one side. Consequently the degree of disorderness will be decrease and hence the entropy.

Hence the correct answer is (D).