Whether an oxidation reaction is endothermic or exothermic?

 Q. Whether an oxidation reaction is endothermic or exothermic?

Ans. Based on the state of the reactants, an oxidation reaction may be exothermic or endothermic. 

As for example, the oxidation reactions of highly reactive metals like sodium and potassium are exothermic reactions.

On the other hand, oxidation of less reactive metals like copper is an endothermic reaction.

Remember :

Generally, oxidation of highly reactive metals are exothermic, whereas oxidation of less reactive metals are endothermic. As for example, highly reactive metals such as sodium, potassium and lithium oxidizes easily. As they are highly flammable in nature, they are kept immersed in the kerosene oil to avoid injuries due to the accidental fire. On the other hand, oxidation of less reactive substance like nitrogen is a type of endothermic reaction.