which kind of reactions tend to be spontaneous
May 9, 2014. Exothermic reactions are spontaneous because the product created by an exothermic reaction is the most stable product. Exothermic reactions release heat or energy. The more energy something has, the more unstable it will be. Therefore kinetics determines that the most stable product will dominate and as a result exothermic reactions are spontaneous to produce a stable product.