# Questions tagged [free-energy]

Also known as Gibbs energy, it is the enthalpy minus the product of thermodynamic temperature and entropy.

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### What is the difference between standard Gibbs energy and Gibbs energy of formation?

Good day guys, I am reading a book on electrochemical engineering, I came across some definitions of Gibbs energy and I am a bit confused as the book does not go into a lot of detail. The book first ...
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### Justifying that Standard Entropy of a Reaction is a Constant of Temperature

One of the parts in a question I'm trying to solve for an assignment goes like this: A key issue in the Hydrogen Economy is Hydrogen Storage. This can be restored if a substance $X$ can bind to $H_2$....
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### Why 40J energy was wasted in case of a non spontaneous process by the system? [closed]

If there is a system which while undergoing a process produced 30J energy and wasted 40J energy therefore the useful energy was -10J and this explains the process was non spontaneous because ∆G is ...
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### Does it make any sense to graph 1/T versus ln(Kc)?

I calculated $K_c$ experimentally for the reaction $$\ce{CO2 + H2O -> H2CO3}$$ at different temperatures. Because $\Delta G =-RT\ln(K)$, I thought that graphing 1/T against $\ln(K_c)$ would give me ...
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### ∆G or ∆G° to predict spontaneity

I have a doubt about using Gibbs free energy to predict the spontaneity of a reaction. It is shown that ∆G = ∆G° + RT ln (Q). That said, in order to predict which direction the reaction spontaneously ...
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### Gibbs Free Energy - Maximum Work

I've been having a lot of trouble trying to truly understand Gibbs free energy from a practical perspective. I have no background in physical chemistry, but I think I have a firm grasp on many of the ...
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### Thermochemical parameters at high temperature

I wanted to calculate Thermodynamic parameters such as Gibbs Free energy, Enthalpy change and Entropy change using Curtis et al explained as this link: https://gaussian.com/wp-content/uploads/dl/...
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### Is there an algebraic form for the textbook reaction coordinate curves?

So here is a curve often used in textbooks to illustrate a reaction coordinate. It's a nice short-hand device to learn the relationship between kinetic and thermodynamic parameters that control the ...
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### Interpretation of Helmholtz energy and Gibbs energy

I know that this question has many other variations on this site, but I'm trying to see if I understood Helmholtz and Gibbs energy properly or not. The material I'm reading from is Physical chemistry ...
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### Why does the reaction of dissolution stop at an equilibrium point? [closed]

The formula for Gibbs free energy is $\Delta G=\Delta H-T\Delta S$. If Gibbs free energy is negative, the reaction is spontaneous. This also applies to dissolution reactions. However, we know that ...
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### Why is glycolysis + lactate fermentation exergonic?

Taking glycolysis and lactic fermentation together, the net reaction (including water!) is simple: Glucose => 2*lactate + energy (the energy is used for ADP+Pi => ATP+H2O) The only changes are: ...
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### Determine enthalpy and entropy from measurements of Kd at different temperatures?

In biochemical experiments, it is very common to measure IC50 (half inhibitory concentration) eg by adding different amounts of an inhibitor to an enzyme+substrate and measuring the reaction rate or ...
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### Is the maximum work done by voltaic cell per mole of reaction? [duplicate]

From the equation $w_{elec,rev}=-nF\Delta E$, and n = the number of moles of electrons transferred in the overall redox reaction, does that make the work per mole of the redox reaction? I am confused ...
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### Why can one set the Gibbs free energy change to 0 when calculating the standard free energy change?

I am trying to understand the following equation: $$\Delta G = \Delta G^{\circ} + RT \ln\left(\frac{[C][D]}{[A][B]}\right)$$ for a reversible reaction with reactants A and B and products C and D. The ...
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### How to estimate the temperature needed to overcome an activation energy barrier?

Trying to elucidate a reaction pathway, I calculated the energies for different transition states possible for that reaction (computational chem. DFT). I found activation free energies ranging from 29 ...
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### Gibbs free energy of mixing in a control volume

I'm trying to model the amount of energy lost due to mixing of a $\mathrm{HCl}$ solution using the Gibbs free energy of mixing. However, I really like a second opinion on the model and the results, ...
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### Is a change in delta-delta-G typically notated as delta-delta-delta-G?

I'm currently writing a research paper, and need to refer to a difference between $\Delta{\Delta}G$s. The naive way to notate this would be $\Delta{\Delta}{\Delta}G$, but that looks cumbersome and ...
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### Equilibrium and endergonic reaction

If a reaction A <-> B has a value of dG°>0, then I know that A -> B is endergonic while A <- B is exergonic. Now if I start with 100% B I could see how equilibrium is reached, B reacts ...