The correct answer is option 1. It increases the rate of reaction.
Generally, a positive catalyst enhances the rate of reaction by decreasing the activation energy. But negative catalyst retards a chemical reaction.
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A positive catalyst, also known simply as a catalyst, is a substance that increases the rate of a chemical reaction without being consumed in the process. It achieves this by providing an alternative reaction pathway with lower activation energy. Here's a detailed description of how a catalyst influences the reaction rate:
1. Lowering activation energy: The primary role of a catalyst is to lower the activation energy required for the reaction to proceed. Activation energy is the barrier that must be overcome for the reactant molecules to convert into products. By providing an alternative reaction pathway, the catalyst reduces the energy required for the reactant molecules to reach the transition state, which is the highest-energy point along the reaction pathway. This lowered activation energy allows a greater fraction of reactant molecules to possess sufficient energy to surpass the barrier and proceed with the reaction.
2. Facilitating reactant interactions: A catalyst facilitates the interaction between reactant molecules by providing a suitable environment or active sites for the reaction to occur. The catalyst's surface or active sites can adsorb reactant molecules, hold them in close proximity, and orient them favorably for bond-breaking or bond-forming processes. This promotes the formation of temporary intermediates or transition states, which subsequently lead to the formation of products. By enhancing the reactant interactions, the catalyst increases the frequency of successful collisions between reactant molecules, leading to an increased reaction rate.
3. Reusability: A critical characteristic of a positive catalyst is that it is not consumed in the reaction. It participates in the reaction but remains unchanged at the end, making it available for further reactions. A small amount of catalyst can facilitate the conversion of many reactants into products since it can be used repeatedly. This reusability and effectiveness in multiple reaction cycles make catalysts highly efficient in increasing the rate of a reaction.
4. Shift in reaction equilibrium (for reversible reactions): In reversible reactions, a positive catalyst can also affect the equilibrium position of the reaction. It speeds up both the forward and reverse reactions to the same extent, enabling the system to reach equilibrium more quickly. While the catalyst does not change the equilibrium constant, it reduces the time required for the reaction to attain equilibrium. This effect is particularly relevant in reversible reactions where the catalyst accelerates the establishment of the equilibrium state.
Overall, a positive catalyst increases the rate of a reaction by lowering the activation energy, facilitating reactant interactions, and being reusable. By providing an alternative reaction pathway, a catalyst enables more reactant molecules to overcome the energy barrier, promoting a faster conversion of reactants into products. The ability of a catalyst to enhance reaction rates without being consumed makes it a valuable tool in various chemical processes and industrial applications. |
