Generic depiction of a nonspontaneous reaction: showing that free energy increases as the reaction progresses on going to products, the products becoming more unstable, energetically, as compared to the reactants. [1]
In chemistry, a nonspontaneous reaction, as contrasted with a spontaneous reaction, is a chemical reaction that under normal conditions will not progress in the forward direction as written because it is not energetically favored, according to the restrictions of the Lewis inequality for natural processes, but can be made to proceed if it is coupled to a driving energy source, such as another strongly exergonic spontaneous reaction mixed into the system.
References 1. Ebbing, Darrell D. (1990). General Chemistry (pg. 730). Houghton Mifflin Co.
