Multiple Choice
Which of the following best explains how catalysts increase the rate of a chemical reaction?
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15. Chemical Kinetics
Factors Influencing Rates
Multiple Choice
Which of the following best describes the effect of increasing the temperature on the rate of a chemical reaction?
A
The reaction rate decreases because molecules move more slowly at higher temperatures.
B
The reaction rate decreases because the activation energy increases with temperature.
C
The reaction rate remains unchanged because temperature does not affect molecular collisions.
D
The reaction rate increases because more molecules have sufficient energy to overcome the activation energy barrier.
Verified step by step guidance1
Understand the relationship between temperature and reaction rate: Increasing temperature generally increases the kinetic energy of molecules.
Recall the Arrhenius equation, which relates the rate constant \(k\) to temperature \(T\):
\[k = A e^{-\frac{E_a}{RT}}\]
where \(A\) is the frequency factor, \(E_a\) is the activation energy, \(R\) is the gas constant, and \(T\) is the temperature in Kelvin.
Recognize that as temperature \(T\) increases, the exponential term \(e^{-\frac{E_a}{RT}}\) increases because the denominator in the exponent becomes larger, making the exponent less negative.
This means more molecules have enough energy to overcome the activation energy barrier, leading to an increased reaction rate.
Therefore, the correct description is that the reaction rate increases because more molecules have sufficient energy to overcome the activation energy barrier.
