The internal energy of the gas decreased by 40 kJ and it performed work of 35 kJ.

The internal energy of the gas decreased by 40 kJ and it performed work of 35 kJ. How much heat did the gas release into the environment as a result of heat exchange?

According to the first law of thermodynamics, the change in the internal energy of the system U is equal to the difference between the heat received Q and the work A by the perfect system. It turns out that you can write down the formula:

U = Q – A.

Let us express from this formula Q:

Q = U + A.

Therefore, since the gas did the work 35 kJ, and the internal energy decreased by 40 kJ, we write:

Q = 35 – 40 = – 5 kJ.

A negative sign indicates that the gas did not receive, but gave up energy. Therefore: he gave 5 kJ.

Answer: the gas released 5 kJ of energy into the environment.