Which term describes a chemical reaction in which a single compound serves as both oxidizing and reducing agent?

• A. Oxidizer
• B. Peroxide Forming
• C. Pyrophoric
• D. Disproportionation

Answer: (D)

Disproportionation is a redox process in which the same compound is simultaneously oxidized and reduced to form two different species. In this type of reaction, the oxidation state of the element involved changes in opposite directions within the same substance, so one portion of the molecules is oxidized while another portion is reduced.

A classic example is the decomposition of hydrogen peroxide: 2 H2O2 → 2 H2O + O2. Here, some of the oxygen ends up more reduced (in water, oxide is at −2), while other oxygen is oxidized (in molecular oxygen, oxidation state is 0). The key idea is that the same compound plays the roles of both oxidizing and reducing agent at the same time.

The other terms don’t capture this internal redox behavior. An oxidizer is simply a substance that accepts electrons, not describing the requirement that the same compound both oxidizes and reduces. Peroxide forming refers to substances that form peroxides, not the internal redox shuffle. Pyrophoric describes materials that ignite spontaneously in air, which is about reactivity with oxygen, not disproportionation. Disproportionation specifically describes a single compound acting as both oxidizing and reducing agent.