If the activation energy required for a chemical reaction were reduced, what would happen to the rate of the reaction?
A. The rate would increase.
B. The rate would decrease.
C. The rate would remain the same.
D. The rate would be zero.
Answer (2)
The problem explores the relationship between activation energy and reaction rate.
The Arrhenius equation ( k = A e − E a / RT ) shows the inverse relationship between activation energy ( E a ) and the rate constant ( k ).
Reducing E a increases the value of e − E a / RT , thus increasing k .
An increased rate constant k implies an increased reaction rate, so the final answer is: The rate would increase.
Explanation
Understanding the Problem The question asks about the effect of reducing the activation energy ( E a ) on the rate of a chemical reaction. We need to determine whether the rate would increase, decrease, remain the same, or become zero.
Recalling the Arrhenius Equation The Arrhenius equation describes the relationship between the rate constant ( k ) of a chemical reaction and the activation energy ( E a ): k = A e − E a / RT where:
k is the rate constant (proportional to the reaction rate),
A is the pre-exponential factor,
E a is the activation energy,
R is the gas constant,
T is the temperature.
Analyzing the Effect of Reducing Activation Energy We need to analyze how the rate constant k changes when E a is reduced. In the Arrhenius equation, E a appears in the exponent with a negative sign. Therefore, decreasing E a will make the exponent less negative, which means the value of e − E a / RT will increase.
Concluding the Effect on Reaction Rate Since k is directly proportional to e − E a / RT , an increase in e − E a / RT leads to an increase in k . Because the rate of the reaction is proportional to the rate constant k , an increase in k means the rate of the reaction will increase.
Final Answer Therefore, if the activation energy required for a chemical reaction is reduced, the rate of the reaction would increase.
Examples
In industrial chemistry, catalysts are used to lower the activation energy of reactions, thereby increasing the rate at which products are formed. For example, in the Haber-Bosch process for synthesizing ammonia, an iron catalyst reduces the activation energy, allowing the reaction to proceed at a faster rate and making the process economically viable. Similarly, in the catalytic converters of cars, platinum and palladium catalysts lower the activation energy for the oxidation of pollutants like carbon monoxide and hydrocarbons, speeding up their conversion to less harmful substances like carbon dioxide and water.
Reducing the activation energy of a chemical reaction results in an increased reaction rate because it allows more reactant particles to collide with sufficient energy. This is described by the Arrhenius equation, where a lower activation energy leads to a higher rate constant. Thus, the correct answer is A: The rate would increase.
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