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I have a major confusion over the relationship between free energy change and the equilibrium constant. I have read that $\Delta G_0= -RT\ln K$.

My first doubt is, does $\Delta G_0$ refer to free energy change ONLY at 25C? Does $\Delta G_0$ make sense for any other temperature?

Secondly, the "T" in the equation Does it also have to be the same temperature as the temperature for which we write $\Delta G_0$? (ie,25C) If not so, can we write any temperature and obtain the corresponding K value?

Please explain.

If 🔼G0 can be defined for other temperatures, does that mean that 🔼S0 and 🔼H0 can also be defined for other temperatures?

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  • $\begingroup$ It can be defined for any temperature. Second part - yes, you write the temperature for which you calculated ΔG at. I'm 99% sure this is a duplicate of something, although I will admit that the exact duplicate is not easy to find, not least because there are like 50 questions on this site with poor unspecific titles like "Gibbs free energy confusion". $\endgroup$ – orthocresol Nov 12 '15 at 11:02
  • $\begingroup$ Sorry about that $\endgroup$ – Newton Nov 12 '15 at 11:08
  • $\begingroup$ It's ok. That's why I chose to give you a brief answer as well. Also yes, standard entropy and enthalpy changes can also be defined for other temperatures. The thermodynamic standard state only stipulates unit activity (which can be approximated by unit concentration) and not a temperature. $\endgroup$ – orthocresol Nov 12 '15 at 11:11
  • $\begingroup$ But I am assuming that pressure should be 1atmosphere? $\endgroup$ – Newton Nov 12 '15 at 11:17
  • $\begingroup$ I have never come across a single book that explains all these small details of thermodynamics $\endgroup$ – Newton Nov 12 '15 at 11:20

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