In a given reversible process, the temperature of an ideal gas is kept constant as the gas is compressed to a smaller volume. Select the true statement from among the following:
A) The gas must absorb heat from its surroundings.
B) The gas must release heat to its surroundings.
C) The pressure of the gas also stays constant.
D) The process is adiabatic.
E) It is impossible to predict on the basis of this data.

Question

Quizplus · Accepted Answer

Since the temperature of the gas is kept constant and the gas is being compressed, its volume and pressure will both decrease. According to the first law of thermodynamics, the change in internal energy of a system is equal to the heat added to the system minus the work done by the system. Since the internal energy of an ideal gas is a function of temperature only, and the temperature is constant, the change in internal energy must be zero. Therefore, the work done by the system in compressing the gas must be exactly balanced by the heat released from the gas to its surroundings. Therefore, the correct statement is that the gas must release heat to its surroundings.

In a Given Reversible Process, the Temperature of an Ideal