Timeline for Can we measure $\Delta G$ when a reaction hasn't reach equilibrium?
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| Dec 14, 2022 at 17:03 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Aug 12, 2022 at 9:00 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Apr 13, 2022 at 21:05 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Dec 6, 2020 at 19:32 | answer | added | pglpm | timeline score: 1 | |
| Dec 6, 2020 at 19:03 | comment | added | pglpm | Just to offer as many points of view as possible to the OP, let me refer to Astarita: Thermodynamics: An Advanced Textbook for Chemical Engineers, especially chapters 2–3. The answer there is: it depends. There are systems for which the free energy doesn't depend on rates of change, even out of equilibrium; and systems for which it does (for example it could depend on the rate of change of volume). In the former case you can measure it out of equilibrium to get its equilibrium value; in the latter case you can't. | |
| Dec 6, 2020 at 18:49 | history | edited | Antonios Sarikas |
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| Oct 17, 2020 at 14:27 | comment | added | Chet Miller | @BobD Using Nonequilibrium thermodynamics, Bird, Stewart, and Lightfoot, Transport Phenomena give the rate of entropy generation from homogeneous chemical reaction as $$\sum_{I=1}^N{\frac{\mu_ir_i}{T}}$$where $\mu_i$ is the chemical potential of species i, and $r_i$ is the molar rate of production of species i per unit volume. See Chapter 24, Section 24.1, The equation of change for entropy | |
| Oct 15, 2020 at 22:27 | comment | added | Chet Miller | @BobD Of course, as the minimum is approached, the rate of entropy generation decreases (I'm guessing, in proportion to the square of the overall reaction rate), so that, in the vicinity of the minimum in G, entropy generation due to deviation from equilibrium strongly approaches zero. | |
| Oct 15, 2020 at 20:08 | comment | added | Chet Miller | I suppose that this approximation would be considered that. | |
| Oct 15, 2020 at 19:46 | comment | added | Bob D | @Chet Miller so you are talking about the realm of non equilibrium thermodynamics? | |
| Oct 15, 2020 at 16:33 | history | edited | Antonios Sarikas | CC BY-SA 4.0 |
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| Oct 15, 2020 at 16:24 | history | edited | Antonios Sarikas | CC BY-SA 4.0 |
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| Oct 15, 2020 at 16:20 | comment | added | Antonios Sarikas | @ChetMiller Can we say therefore that the thermodynamic potentials such as $G$, $U$, $H$ etc. can be well defined (we can measure them) even if the system is not in equilibrium? Because for example we can measure $U$ in principle (the sum of kinetic and potential energy) even if the system hasn't fixed temperature pressure etc . | |
| Oct 15, 2020 at 14:09 | comment | added | Chet Miller | Yes, if you accept the idea that, even if the system is not quite at equilibrium, you can still calculate its Gibbs free energy. Some people would balk at this, but, personally, not me. We do this all the time when we use the open system, time dependent version of the first law of thermodynamics, with respect to U. | |
| Oct 15, 2020 at 13:23 | answer | added | Bob D | timeline score: 0 | |
| Oct 15, 2020 at 12:23 | history | asked | Antonios Sarikas | CC BY-SA 4.0 |