How Do Catalysts Affect Enthalpy in Reactions?

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Discussion Overview

The discussion revolves around the effect of catalysts on enthalpy in chemical reactions, focusing on the relationship between activation energy and enthalpy change. Participants explore theoretical aspects of enthalpy, activation energy, and the role of catalysts in reaction pathways.

Discussion Character

  • Conceptual clarification, Homework-related, Technical explanation

Main Points Raised

  • One participant states that catalysts decrease the activation energy of a reaction and questions how this affects enthalpy.
  • Another participant asserts that while catalysts lower the activation enthalpy, they do not change the overall enthalpy of the reaction, which is defined by the difference between initial and final states.
  • A further clarification is made regarding the constancy of initial and final states, suggesting that while activation energy is reduced, the change in enthalpy (ΔH) remains the same for reactions with or without a catalyst.

Areas of Agreement / Disagreement

Participants generally agree that the enthalpy change of a reaction remains unchanged by the presence of a catalyst, though some nuances regarding activation energy and enthalpy definitions are discussed.

Contextual Notes

Participants reference state functions and the definitions of activation energy and enthalpy without resolving potential ambiguities in these concepts.

brake4country
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Homework Statement


This question is just for an overall understanding of enthalpy and activation. My book states that catalysts decrease the activation energy of a reaction. This makes sense. However, how does this change the enthalpy? If a catalyst creates a new pathway, wouldn't the enthalpy change be different as compared to the reaction without a catalyst? Thanks in advance.

Homework Equations


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The Attempt at a Solution

 
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brake4country said:
However, how does this change the enthalpy?
It doesn't change the enthalpy of the reaction. It does change the activation enthalpy of the reaction.

Enthalpy of a reaction is the difference in enthalpies only between the initial and final states. Activation energy or activation enthalpy is the maximum energy change on the path the reaction takes between those initial and final states.
 
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Oh I get it but let me be clear. Initial and final states (as defined by state functions) will be the same regardless if the reaction uses a catalyst. Thus Ea is lower but the ΔH for both will be the same?
 
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Thank you!
 

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