A Level Chemistry OCR Practice Exam

Which type of redox reaction involves the oxidation and reduction of the same element?

1. Synthesis reaction

2. Displacement reaction

3. Disproportionation

4. Combustion reaction

The correct answer is: Disproportionation

The correct answer is indeed disproportional reaction. This type of redox reaction is unique in that it involves a single element being both oxidized and reduced in different parts of the reaction. In a disproportionation reaction, the same element undergoes two simultaneous reactions, one where it loses electrons (is oxidized) and another where it gains electrons (is reduced). A classic example is the reaction of chlorine gas (\(Cl_2\)) with water, where chlorine can form both chloride ions (\(Cl^-\)) and hypochlorous acid (HClO). Other types of reactions listed do not involve an element being oxidized and reduced in the same reaction. Synthesis reactions typically involve the combination of two or more substances to form a single product, while displacement reactions involve one element replacing another in a compound. Combustion reactions refer to the burning of a substance in the presence of oxygen, usually resulting in the formation of oxides without the same element undergoing both oxidation and reduction.