The reaction is described as spontaneous because it favors the products and releases free energy. Being classified as a spontaneous reaction would mean that the reaction of the reactants is happening as soon as these substances are in contact. They do not need any supply of energy for them to reach the activation energy. The total energy of the reactants is equal or more than that of the activation energy. The reaction being described is a combustion reaction where an organic compound reacts with oxygen forming CO2 and water. Generally, this type of reaction is a spontaneous reaction and is exothermic.
