Question

A gas is compressed, resulting in 74J of work done. Simultaneously, 26J of heat is given off to the surroundings. Calculate the change in energy of the gas.

a) 48J
b) 100J
c) -48J
d) -100J

Answer 1

The change in energy of the gas, when compressed with work done of 74J and heat given off of 26J, is -100J.

Step-by-step explanation:

When a gas is compressed and work is done on it, its internal energy increases. In this scenario, 74J of work is done on the gas. However, if heat is also transferred out of the gas to the surroundings, this will decrease its internal energy. Given that 26J of heat is given off, the overall change in energy of the gas can be calculated 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

Here, since work is done on the gas, we consider W as positive and since heat is given off from the gas, Q is negative:

ΔU = -26J - 74J = -100J

Therefore, the change in energy of the gas is -100J.