Question

An ideal gas is compressed isothermally from 30 L to 20 L. During this process, 6 J of energy is expended by the external mechanism that compressed the gas. What is the change of internal energy for this gas?

A) -12 J
B) zero
C) +12 J
D) +6 J
E) -6 J

Answer 1

The change in internal energy of an ideal gas is equal to the work done by the system. In an isothermal process, the change in internal energy is equal to the opposite of the work done by the system. In this case, the change in internal energy is -6 J.

Step-by-step explanation:

The change in internal energy of an ideal gas can be determined using the First Law of Thermodynamics, which states that the change in internal energy (ΔU) of a system is equal to the heat (Q) added to the system minus the work (W) done by the system:

ΔU = Q - W

In this case, the process is isothermal, which means the temperature of the gas remains constant. Since the change in internal energy is equal to the energy transferred as heat minus the work done by the system, and the process is isothermal, the change in internal energy is equal to the opposite of the work done by the system:

ΔU = -W

Given that 6 J of energy is expended by the external mechanism that compressed the gas, the change in internal energy of the gas is -6 J. Therefore, the correct answer is E) -6 J.