What is the role of an oxidising agent in a chemical reaction?

The role of an oxidising agent in a chemical reaction is to accept electrons from another substance, which results in the oxidation of that substance. This process often involves the oxidising agent gaining oxygen or losing hydrogen, effectively increasing its oxidation state. When the oxidising agent gives oxygen to another substance, it facilitates the transfer of electrons, thereby causing the reduction of that substance.

This electron transfer is central to redox reactions, where one species is oxidised (loses electrons) and another is reduced (gains electrons). Therefore, the correct answer highlights the dual role of an oxidising agent in either adding oxygen to a reactant or removing electrons from another reactant, both of which are crucial for facilitating oxidation.

The other options do not accurately capture the full definition of an oxidising agent. For instance, while the first option suggests the agent takes oxygen, it does not convey the important aspect of electron transfer. The third option incorrectly limits the agency of oxidising agents to only reducing other substances, which contradicts their fundamental definition. Finally, the fourth option implies that the oxidising agent is inactive, which is not reflective of its critical participatory role in the reaction.