Question

Two moles of helium gas are placed in a cylindrical container with a piston. The gas is at room temperature 25°C and under a pressure of 3.0×10⁵Pa. When the pressure from the outside is decreased while keeping the temperature the same as the room temperature, the volume of the gas doubles. (a) Find the work the external agent does on the gas in the process.

The work the external agent does on the gas is:
a. Positive
b. Negative
c. Zero
d. None of these

Answer 1

The work done by an external agent on helium gas that doubles in volume at constant temperature is negative since the gas is performing work on the surroundings.

Step-by-step explanation:

To determine the work done by an external agent on a gas, we use the formula W = -P∆V, where W is the work done, P is the external pressure, and ∆V is the change in volume. In the given scenario, the volume of the helium gas doubles while the pressure and temperature remain constant.

Since the external pressure is decreasing to allow the gas to expand, the gas does work on the surroundings, meaning the work done by the external agent is negative. Therefore, the correct answer is (b) Negative.