# Questions tagged [thermodynamics]

Applicable to questions about heat, energy, work, and their interconversion in chemistry. See the tag wiki for a detailed list of topics. Questions tagged may also be tagged with [enthalpy], [energy], [free-energy] where appropriate.

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### Calculating ΔG at the extremes of reaction extent

This question follows on from a great post on comparing $\Delta_\mathrm{r} G^{\circ}$ to $\Delta_\mathrm{r} G$ answered here The G vs ξ graph that is used in the answer is an excellent tool to ...
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### Can somebody explain the low temperature Schottky anomaly for two level systems?

Statistical thermodynamics question. Can somebody explain the low temperature Schottky anomaly for two level systems? Why is this anomaly not seen in all materials?
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### If change in free energy (G) is positive, how do those reactions still occur?

I was doing a couple of problems for homework: Calculate $K_\mathrm{sp}$ of $\ce{AgI}$ at $55.0\ \mathrm{^\circ C}$ Calculate $K_\mathrm{b}$ of $\ce{NH3}$ at $36.0\ \mathrm{^\circ C}$ I have to use ...
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### Gibbs free energy of activation and activation energy [duplicate]

What the difference between Gibbs free energy of activation and activation energy
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### Calculating melting temperature of water with thermodynamical data

So at zero degrees celsius($\pu{273 K}$), for clean water, we have the equilibrium eq.: $\ce{H2O(s) = H2O(l)}$ As it is at equilibrium, we know that $\Delta G = 0$. As we are dealing with clean ...
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### Is temperature double-counted in the Gibbs free energy equation?

Complete amateur here. When looking at one form of the equation deriving the change in Gibbs free energy for a given chemical reaction, the terms change in enthalpy, and the negative product of ...
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### Thermodynamics behind organic chemical reactions? [closed]

I took organic chemistry a few years ago at my university, and although I went through the motions to pass the exams, I didn't understand the thermodynamic reasoning behind why the reactions actually ...
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### Why do we use external pressure when calculating work done by gas? [duplicate]

For irreversible expansion and compression, why is dw= -pextdV but not dw= -pdV ? Many of the texts and related questions on this site I encountered give a same general idea: because work done= ...
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### Trying to understand rationale behind Joule-Thomson experiment

The purpose of the original Joule (as opposed to JT) expansion experiment was to assess intermolecular interactions in real gases. In that experiment, Joule immersed twin glass globes into a water ...
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### How to measure quantities at standard state when this state is a hypothetical one?

Consider the reaction $$\ce{A(g) + H2O(l) <=> B(aq) + C(g)}$$ If all gases and solutions were ideal, the standard state would be pure water, the solute B at a concentration of 1 M, the gases A ...
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### Change in heat of photosynthesis

Consider a plant that uses the energy it receives from the sun to do work (to undergo photosynthesis) to produce glucose. The minimum amount of work this plant can do to produce 1 mole of glucose is ...
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### Gibbs Free Energy Notation

What's the difference between $G$, $\Delta G$, $\Delta G^\circ$, and $\Delta_\mathrm r G^\circ$? I've seen the first two used interchangably, and seen $G$ specifically referred to as change in Gibbs ...
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### Which quantities change when choosing a different standard state?

Chemistry and biochemistry use a different standard state. For example, the standard hydrogen ion concentration is the one at pH = 0 in one case, and the one at neutral pH in the other case. Which ...
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### Derivation of relationship betwee standard Gibbs energy of reaction and equilibrium constant? [closed]

How does one derive $\Delta_\mathrm r G^\circ = -RT\ln(K)$? I don't see the connection mathematically or conceptually; how does Gibbs at all relate to the equilibrium constant of a reaction? This was ...
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### Do electrons go to even lower ground states after exothermic reactions?

I am a bit confused about what happens to the energy levels during an exothermic reaction. I understand that during an exothermic reaction, the energy of the electrons decreases. Is the potential ...