Why Do Enthalpy and Entropy Changes Often Seem Temperature-Independent?

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Discussion Overview

The discussion centers on the temperature dependence of enthalpy and entropy changes in chemical reactions, exploring whether these changes can be assumed to be constant across different temperatures. The scope includes theoretical considerations and conceptual clarifications relevant to thermodynamics.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions why enthalpy and entropy changes are often treated as temperature-independent.
  • Another participant emphasizes the need for prior understanding and asks if the enthalpy and entropy of reactants and products are indeed constant or if they vary with temperature.
  • A third participant notes that the assumption of temperature independence is a simplification encountered in early undergraduate chemistry, suggesting that real thermodynamics reveals more complexity.
  • This same participant mentions that in certain cases, the change in enthalpy may be small enough that a weighted average can be used, implying variability in temperature effects.
  • A later reply seeks further clarification on the reasoning behind the simplification.

Areas of Agreement / Disagreement

Participants express differing views on the assumptions regarding temperature dependence, with some suggesting it is a simplification while others question the validity of this approach. The discussion remains unresolved regarding the extent to which enthalpy and entropy changes are affected by temperature.

Contextual Notes

Limitations include the potential variability of enthalpy and entropy with temperature, the lack of consensus on the applicability of simplifications, and the dependence on specific definitions and contexts within thermodynamics.

kasse
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Why is it that the change in enthalpy and entropy of a reaction often can be assumed not to depend on temperature?
 
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You've been posting long enough to know that you must do your work before anyone can help you. So what are your thoughts on the matter? Are the enthalpy and entropy of reactants and products constant? If they change with temperature, is the rate of change the same for all reactants and products?
 
It is a simplification in early undergrad chemistry. When you get to real thermodynamics, you will see that this is not true, they will give you the tools then that will aid you.

Although in some cases the change in enthalphy is so small according to temperature that you can use a weighted value.
 
But why?
 

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