A Level Chemistry OCR Practice Exam

What defines an oxidising agent in a chemical reaction?

1. A reagent that loses electrons

2. A reagent that takes electrons from another species

3. A reagent that becomes reduced

4. A reagent that is unchanged after the reaction

The correct answer is: A reagent that takes electrons from another species

An oxidising agent is defined as a reagent that takes electrons from another species during a chemical reaction. This process results in the oxidation of that species, while the oxidising agent itself undergoes a reduction, gaining electrons in the process. The defining characteristic of an oxidising agent is its ability to accept electrons, thereby facilitating the oxidation of the other substance involved in the reaction. For instance, when looking at common oxidising agents like potassium permanganate or dichromate ions, their function in redox reactions highlights this role. They accept electrons from the substance that is being oxidised, leading to their own reduction. The other options, while related to aspects of redox processes, do not accurately capture the primary function of an oxidising agent. A reagent that loses electrons describes a reducing agent, while a reagent that becomes reduced is essentially just stating what happens to an oxidising agent without defining its role specifically in the context of the reaction. Lastly, a reagent that is unchanged after the reaction does not correctly apply to oxidising agents, as they typically undergo transformation during the electron transfer process.