The Question is from neet-chemistry surface-chemistry , and it was created by the author Mr. S M HUSSAIN

Question

A catalyst alters the rate of a chemical reaction by:

Mr. S M HUSSAIN · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Catalysis and Reaction Kinetics
 **Related Topics**: Activation energy, reaction rate, equilibrium constant
 **Prerequisites**: Understanding of chemical kinetics and the concept of activation energy.
## SOLUTION PATHWAY
**Given Information**:
The question asks how a catalyst affects the rate of a chemical reaction.
**Method & Steps**:
1. Understanding the role of a catalyst:
A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It does this by providing an alternative reaction pathway with a lower activation energy.
  Reasoning: Catalysts do not shift the equilibrium position of a reaction; they only speed up the rate at which equilibrium is reached.
  Formula/Rule:  None directly applicable, but the Arrhenius equation ($k = Ae^{-E_a/RT}$) demonstrates the relationship between rate constant (k), activation energy ($E_a$), and temperature (T).
 2. Analyzing the options:
Option A is incorrect because catalysts do not shift the equilibrium. They affect the rate of both forward and reverse reactions equally.
Option B is incorrect because catalysts do not change the concentration of reactants. They only provide an alternative reaction pathway.
Option C is correct because catalysts lower the activation energy ($E_a$) of the reaction, making it easier for reactants to overcome the energy barrier and form products.  This leads to a faster reaction rate.
Option D is incorrect because catalysts do not change the enthalpy change ($\Delta H$) of the reaction. The enthalpy change is a thermodynamic property that depends only on the initial and final states of the reaction.
 3. Conclusion:
A catalyst alters the rate of a chemical reaction by changing the activation energy of the reaction.
  Result: Option C
  Verification: The effect of a catalyst on reaction rate is well-established in chemical kinetics. Lowering the activation energy directly leads to an increased rate constant, and thus a faster reaction rate.
 ## OPTION ANALYSIS
A :x: Shifting the equilibrium is not the primary mechanism by which a catalyst affects reaction rates. While equilibrium is eventually reached faster, the position of equilibrium remains unchanged.
B :x: Catalysts do not increase reactant concentration; they accelerate the rate at which reactants are converted to products.
C ✓: Correct. Catalysts work by providing an alternative reaction pathway with a lower activation energy. This speeds up the reaction.
D :x: Catalysts do not affect the overall enthalpy change of the reaction; they only affect the kinetics.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing the effect of a catalyst on reaction rate with its effect on equilibrium: Catalysts affect the rate, not the equilibrium constant.
  2.Thinking catalysts are consumed in the reaction: Catalysts are regenerated at the end of the reaction.
 **Quick Tips**:
  1.Remember that catalysts lower the activation energy, making it easier for the reaction to proceed.
  2.Visualize the energy profile diagram of a reaction with and without a catalyst to understand the effect on activation energy.

Mr. S M HUSSAIN · Answer

Shifting the equilibrium towards product formation.

Mr. S M HUSSAIN · Answer

Increasing the concentration of reactants.

Mr. S M HUSSAIN · Answer

The correct Option is "Changing the activation energy of the reaction."

Mr. S M HUSSAIN · Answer

Altering the enthalpy change of the reaction.

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