What happens to promoters or poisons during a catalyzed reaction?


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> [Catalysts](https://en.wikipedia.org/wiki/Catalysis) are substances that influence reaction rates without undergoing changes in their mass and chemical composition, but may undergo physical changes.
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Promoters, poison etc. affect the activity of the catalyst. What are some examples of promoters or poison undergoing a change (physical or chemical) during a chemical reaction?


