Question

A gas expands and does PV work on its surroundings equal to 344 J. At the same time, it absorbs 139 J of heat from the surroundings. Calculate the change in energy of the gas. Note: PV work means work done by a changing volume against constant pressure. Enter your answer in scientific notation.

Answer 1

Explanation:

According to first law of thermodynamics, total energy of a system and its surroundings remain constant.

Equation for first law of thermodynamics is as follows.

             $\Delta U = q + w$

where,       $\Delta U$ = change in energy

                                q = heat released or absorbed

                                 w = work done

As it is given that heat absorbed is 139 J (as heat is absorbed so it will be positive) and work done is -344 J (as work is done on the system).

Hence, we will calculate the energy change as follows.

                    $\Delta U = q + w$

                                 = 139 J + (-344 J)

                                 = 205 J

Thus, we can conclude that change in energy of the gas is 205 J.