Difficulty: Easy

Average Score: 77%

Which of the following would increase the rate of an endothermic reaction?

Rationale

Increasing the concentration of reactants would increase the rate of an endothermic reaction.

In an endothermic reaction, the system absorbs heat from the surroundings, and increasing the concentration of reactants enhances the likelihood of collision between reactant molecules. This increased collision frequency can lead to a greater rate of reaction, making it more favorable for the endothermic process to occur.

A (Decreasing contact area of reactants) YOUR ANSWER

Decreasing the contact area of reactants reduces the surface area available for collisions to occur. This limitation directly diminishes the frequency of interactions between molecules, thereby lowering the rate of the reaction. In contrast, maximizing contact area is essential for enhancing reaction rates.

B (Increasing the concentration of products) YOUR ANSWER

Increasing the concentration of products can shift the equilibrium position towards the reactants in a reversible reaction, according to Le Chatelier's principle. This shift may ultimately decrease the rate of the forward endothermic reaction, as it counteracts the formation of reactants, thereby not contributing to an increased reaction rate.

C (Decreasing the temperature) YOUR ANSWER

Decreasing the temperature generally reduces the kinetic energy of the molecules involved in the reaction, leading to fewer effective collisions between reactants. For endothermic reactions, which require heat absorption, lowering the temperature is counterproductive and would decrease the reaction rate rather than increase it.

D (Increasing the concentration of reactants) CORRECT

Increasing the concentration of reactants enhances the number of molecules available for collisions, thereby increasing the reaction rate. This is particularly beneficial in endothermic reactions, as it promotes a higher likelihood of successful interactions that can lead to the absorption of energy and formation of products.

Conclusion

In summary, the rate of an endothermic reaction can be effectively increased by elevating the concentration of reactants, which boosts collision frequency and reaction likelihood. The other options—decreasing contact area, increasing product concentration, and lowering temperature—would either hinder the reaction or slow it down, underscoring the importance of reactant concentration in driving endothermic processes forward.

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