Homework 8.9 [ENDORSED]

[Angela_Kim_1N]

A piston confines 0.200 mol Ne(g) in 1.20 L at 25 degrees C. Two experiments are performed. (a) The gas is allowed to expand through an additional 1.20 L against a constant pressure of 1.00 atm. (b) The gas is allowed to expand reversibly and isothermally to the same final volume. Which process does more work?

How do we know that part a is an irreversible expansion?

[Rochelle Ellison 2H]

In a reversible expansion the surrounding's pressure would not be constant and the system would have to be at equilibrium with the surroundings meaning that they would have the same pressure since a reversible expansion is defined as a process where infinitely small changes in the external or internal pressures cause changes in the volume to be infinitely small. In part a, the problem states that the expansion occurs against a constant pressure of 1 atm and the pressure of the system is (0.2 mol)(0.08206 L*atm/mol*K)(298.15K)/(1.2 L) = 4.08 atm so the pressures are clearly different. Therefore, even without an infinitely small change in either pressure, the gas will expand rapidly and irreversibly because of its greater pressure.

[Joslyn_Santana_2B]

Will we be given the conversion factor from torr to atm on the formula sheet?

[Nikhil_Madan_3C]

The gas constant should be given in different units (J*K^-1*mol^-1, L*atm*K^-1*mol^-1, L*atm*K^-1*mol^-1, L*bar*K^-1*mol^-1, L*Torr*K^-1*mol^-1).