Two moles of an ideal gas expand freely into vacuum. The work done by the gas is A. 2J B. 4J C. Infinity D. 0

The correct answer is D.

Work is done by a force acting through a distance. In this case, the force is the pressure of the gas acting against the walls of the container. The distance is the change in volume of the gas.

When an ideal gas expands freely into a vacuum, the pressure of the gas is zero. This is because there are no walls to push against. Therefore, the work done by the gas is also zero.

Option A is incorrect because it assumes that the pressure of the gas is non-zero. Option B is incorrect because it assumes that the change in volume of the gas is non-zero. Option C is incorrect because it is not possible for the work done by the gas to be infinite.