The negative ion reactions that consist of the formation of carbon dioxide in the atmosphere is generally an exothermic reaction. By definition, an exothermic reaction takes place when the chemical process eventually releases heat as its by-product. It is in contrast in endothermic process wherein heat is absorbed.
Enthalpy of Formation (): It is defined as change in enthalpy when one mole of substance is formed at standard temperature and pressure from its pure elements under same conditions.
1)
When the energy is released during formation of compound in a chemical reaction that is an Exothermic reaction.
2)
When the energy is absorbed during the formation of compound in a chemical reaction that is an Endothermic reaction
The of formation of carbon dioxide is negative means that the reaction is exothermic reaction.