Scelta multipla
How does the presence of a catalyst affect the enthalpy change (ΔH) of a chemical reaction?
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15. Chemical Kinetics
Catalyst
Scelta multipla
Which of the following best describes the usefulness of catalysts in chemical reactions?
A
They change the equilibrium position of a reaction.
B
They are consumed during the reaction and become part of the products.
C
They increase the yield of products by providing more reactants.
D
They increase the rate of a reaction by lowering the activation energy.
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Understand the role of a catalyst in a chemical reaction: a catalyst provides an alternative reaction pathway with a lower activation energy, which increases the rate at which the reaction reaches equilibrium.
Recall that catalysts do not change the equilibrium position of a reaction; they only help the system reach equilibrium faster without affecting the concentrations of reactants and products at equilibrium.
Recognize that catalysts are not consumed in the reaction; they remain unchanged after the reaction and can be used repeatedly.
Note that catalysts do not increase the amount of reactants or products; they only affect the speed of the reaction, not the overall yield or equilibrium composition.
Conclude that the best description of a catalyst's usefulness is that it increases the rate of a reaction by lowering the activation energy, facilitating faster attainment of equilibrium.
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