Oxygen weighing 2 kg occupies a volume of 6 m^3 and is under a pressure of 1 atm. The gas was heated first at constant pressure to a volume of 13 m^3, and then at constant volume to a pressure of 23 atm. Find the change in the internal energy of the gas.

Detailed solution with a brief record of the conditions, formulas and laws used in the solution, derivation of the calculation formula and answer.
If you have any questions regarding the solution, please write. I try to help.