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

In summary, the assumption that the change in enthalpy and entropy of a reaction does not depend on temperature is a simplification commonly used in early undergraduate chemistry. However, in more advanced thermodynamics, it is not always true and tools are provided to calculate more accurate values. This assumption is often used because the change in enthalpy may be negligible compared to other factors.
  • #1
kasse
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1
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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  • #2
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?
 
  • #3
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.
 
  • #4
But why?
 

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

What is enthalpy?

Enthalpy is a thermodynamic property that describes the total energy of a system. It takes into account both the internal energy and the work done by or on the system.

How does enthalpy change during a chemical reaction?

In a chemical reaction, the enthalpy can either increase or decrease. An increase in enthalpy is called an endothermic reaction, where energy is absorbed from the surroundings. A decrease in enthalpy is called an exothermic reaction, where energy is released to the surroundings.

What is entropy?

Entropy is a measure of the disorder or randomness in a system. It is a thermodynamic property that increases with the number of microstates available to a system.

How does entropy change during a physical process?

In a physical process, like melting or vaporization, the entropy of a system increases because the number of microstates increases as the molecules become more disordered.

What is the relationship between enthalpy and entropy?

The relationship between enthalpy and entropy is described by the Gibbs free energy equation, ΔG = ΔH - TΔS. This equation shows that for a spontaneous reaction to occur, there must be a decrease in enthalpy and an increase in entropy.

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