# Questions tagged [entropy]

For questions about the thermodynamical state function entropy, commonly understood as a measure of disorder.

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### How do you use entropy and enthalpy to explain how chemical reactions come to equilibrium?

Let's say I have a reversible chemical reaction between A and B that will come to equilibrium in a closed system. How do I use the concepts of enthalpy, entropy and naturally then, Gibbs free energy, ...
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### Can Gibbs Free Energy equation be used to explain why some phase changes are exothermic or endothermic?

I was wondering about some ways to explain why some phase changes are exo / endo. I am aware that for endothermic phase changes (boiling, melting, sublimation) energy input is required to raise the ...
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### Is the entropy change positive or negative in this reaction?

Suppose I have a reversible reaction \begin{align} \ce{A(g) + B(g) <=> C(g)}\\ \end{align} with equilibrium constant K. Its ΔΗ is positive throughout. Now, suppose I start with 1 mole ...
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### Spontaneity criterion for phase transformations and chemical reactions [closed]

Why is the Gibbs free energy (G) considered a spontaneity criterion for phase transformations and chemical reactions? Why are other thermodynamic parameters such as enthalpy (H), entropy (S), and ...
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### Why is rapid expansion/compression reversible?

I am looking over the Otto Cycle on this MIT website and it says at one point "the processes from 1 to 2 and from 3 to 4 are isentropic" in reference to the expansion and compression of the ...
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### What does it mean that the standard molar entropy value is the amount of energy that a substance must have to exist at a certain temperature?

What does it mean that the standard molar entropy value is the amount of energy that a substance must have to exist at a certain temperature? According to this reference: http://khimiya.org/volume15/...
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