Forward vs Reverse Reaction (both endo/exo thermic)

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Discussion Overview

The discussion centers on whether both the forward and reverse reactions in a chemical process can be endothermic or exothermic, or if they must always exhibit opposite enthalpy changes. The scope includes theoretical considerations of thermodynamics and enthalpy as a state function.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant questions if both the forward and reverse reactions can be endothermic or exothermic, suggesting a potential for them to be the same.
  • Another participant raises the concept of energy conservation in relation to the reactions.
  • Some participants assert that both reactions cannot be exothermic or endothermic, citing that enthalpy (H) is a state function. They explain that the enthalpy change in any process is independent of the path taken, leading to the conclusion that if the forward reaction is exothermic, the reverse must be endothermic, and vice versa.
  • One participant provides a mathematical expression to support their claim about the relationship between forward and reverse enthalpy changes, stating that the enthalpy change for the forward reaction is equal in magnitude but opposite in sign to that of the reverse reaction.

Areas of Agreement / Disagreement

Participants generally agree that the forward and reverse reactions cannot both be exothermic or endothermic, but there is a lack of consensus on the implications of energy conservation and the broader context of the reactions.

Contextual Notes

The discussion does not resolve the implications of energy conservation in relation to the enthalpy changes, nor does it clarify the specific conditions under which these reactions are considered.

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Can both the forward and reverse reaction be endothermic or exothermic? Or must they ALWAYS be inverse one another?

Thanks
 
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What about energy conservation?
 
They cannot both be exothermic or endothermic. Enthalpy (H) is a state function. This means that the enthalpy of a system is completely independent of how one arrived at that system. It's like mass. It follows from this that the enthalpy change in any process is expressed by:

H_{final}-H_{initial} = \Delta\ H

for all processes. So if the forward process has a negative change in enthalpy (exothermic), the reverse process will have a positive change in enthalpy of equal magnitude. For a reverse reaction, you just switch the "final" and "initial" states, which amounts to multiplying the left by negative one. So this equation relates forward and reverse processes:

H_{for}= -H_{rev}

EDIT:
Sorry I can't get LaTex to work right, I'm new to this.
 
Last edited:
horsecandy911 said:
They cannot both be exothermic or endothermic. Enthalpy (H) is a state function. This means that the enthalpy of a system is completely independent of how one arrived at that system. It's like mass. It follows from this that the enthalpy change in any process is expressed by:

H_{final}-H_{initial} = \Delta\ H

for all processes. So if the forward process has a negative change in enthalpy (exothermic), the reverse process will have a positive change in enthalpy of equal magnitude. For a reverse reaction, you just switch the "final" and "initial" states, which amounts to multiplying the left by negative one. So this equation relates forward and reverse processes:

H_{for}= -H_{rev}

Good answer on this. I appreciate it. Thanks!
 

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