A Level Chemistry OCR Practice Exam

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Prepare effectively for the A Level Chemistry OCR Exam with our valuable resources, including multiple choice questions and hints. Unlock your potential and ace your exam with comprehensive practice materials designed for your success!

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What is the main role of a catalyst in a chemical reaction?

To change the final product
To increase the temperature of the reaction
To increase the rate of reaction without being consumed
To act as a reactant

The correct answer is: To increase the rate of reaction without being consumed

The main role of a catalyst in a chemical reaction is to increase the rate of reaction without being consumed in the process. A catalyst achieves this by providing an alternative pathway for the reaction to occur, which has a lower activation energy than the uncatalyzed reaction. This allows more reactant molecules to have sufficient energy to react at a given temperature, leading to an increase in the reaction rate. Importantly, after the reaction has occurred, the catalyst remains unchanged in its chemical composition and can be used repeatedly in subsequent reactions. This characteristic sets catalysts apart from reactants, which are consumed during the reaction, and from products, which are formed as a result of the reaction. The ability to speed up reactions without being used up makes catalysts essential in various industrial processes and helps improve efficiency in both chemical reactions and energy use.