2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/83864In the previous papers of the author it has been shown that the 1st law of thermodynamics in chemical reactions is the following one: dU=dQ+PdV+SUM In the present paper this theory was developed and it has been shown that the 1st law of thermodynamics in chemical reactions has the following form: dC=-dU+dA and -dU=dQ where dC is the change in the chemical energy, dU is the change in the internal energy. Internal energy is the energy of thermal motion of molecules.e-mail me istepanov@email.com, 6 pagesGeneral PhysicsChemical Physicstext