In a thermochemical equation, the enthalpy change is always written next to the balanced chemical equation.
For example, chemical reaction: 2Mg + O₂ → 2MgO. ΔH = -1204 kJ; this is exothermic reaction,
or chemical reaction: Fe₂O₃(s) + 3CO(g) → 2Fe(s) + 3CO₂(g);ΔH = + 26.3 kJ, ths is endothermic reaction.
There are two types of reaction: endothermic reaction (chemical reaction that absorbs more energy than it releases) and exothermic reaction (chemical reaction that releases more energy than it absorbs).