# Questions tagged [entropy]

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

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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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### Is there an equivalent term for favourable and non-favourable entropy?

For Gibbs energy, we have 'exergonic' or 'endergonic' For Enthalpy, we have 'exothermic' or 'endothermic' It seems logical there should be an equivalent pair of terms for entropy, but I can't seem to ...
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### Effect of degree of freedom on entropy change during a reaction

In the reaction $$\ce{C_{(s)} + O2_{(g)} -> CO2_{(g)}}$$ one mole gaseous reactant gives one mole gaseous product, so there is no significant change in entropy. It can be verified by line of \$\ce{...
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### In regards to the Gibbs free energy equation, it seems that the two terms oppose one another, Enthalpy and -TS. Can you explain this?

So for example, if H is endothermic, then the enthalpy term is positive, meaning energy is absorbed by system overall, meaning net bonds broken, meaning the equation leans towards nonspontaneity. If ...