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

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How to determine the value for n in the Gibbs free energy and redox potential equation?

I am having a problem with this equation for redox potentials $$\Delta G=-nF\Delta E$$ In this equation I never am totally sure about what the value of $n$ should be, for example for the reaction ...
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What is the precise definition of W$_{max}$ in the context of electrochemistry and thermodynamics?

I'd like clarification of the meaning of $W_\mathrm{max}$ in the following equations (and thus in the combined result in the third equation): \begin{align} W_\mathrm{max} &= \Delta G\\ ...
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What is the difference between ΔG and ΔG “with an o on top”?

I want to know the difference between $\Delta G$ and $\Delta G$ "with an o on top"? I couldn't figure it out. Ex: $\Delta G^\circ = -RT\ln K$ $\Delta G = \Delta G^\circ + RT \ln K$ What is the ...
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Truly Understanding the Second Law of Thermodynamics and Entropy

There are some seemingly contradictory things I'd like cleared up: Second Law states: dSUniv = dsSys + dsSurr, and dSUniv is always positive in a spontaneous process. First off, what does ...
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Why does water evaporate spontaneously at room temperature despite dG > 0?

Standard Gibbs free energy of formation of liquid water at 298 K is −237.17 kJ/mol and that of water vapour is −228.57 kJ/mol. Therefore, $$\ce{H2O(l)->H2O(g)}~~\Delta G=8.43~\mathrm{kJ/mol}$$ ...
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Spontaneous Reaction and Gibbs Free Energy

I know how to derive the expression for the equilibrium constant starting from $dG=0$, $$\ln(K)=-\frac{\Delta G ^o}{RT}$$ However, if we are not at equilibrium, $dG$ is not necessarily zero. In this ...
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52 views

If Gibbs energy of activation is positive, how is the change to the transition state possible?

The Gibbs energy increases from the reactants to the transition state, but according to the Second Law of Thermodynamics, entropy of the universe can only increase. Why is the transition state ...
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181 views

What is non-expansion work?

I learnt that Gibbs free energy is the maximum amount of non-expansion work. But the phrase non expansion work confuses me. Work is defined as pressure times change in volume. If there is no ...
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32 views

Heat Capacity temperature dependence and Gibbs energy

I got this problem in school as a tool to get ready for International Chemistry Olympiad, but I have some problems with this challenge. So, the problem is to calculate as precise as possible the Gibbs ...
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91 views

Relative energies between reactants and products

I've been asked to draw a relative energy sketch of the reactants and the two products. The reaction being examined was adding copper acetate monohydrate to glycine in two different fashions to create ...
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56 views

Are all naturally occuring reactions exothermic?

If a reaction is endothermic, then the reaction must take energy from the environment to occur (as far as I know), and if this is the case, then to me the reaction seems energetically unfavorable, as ...
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105 views

Where to find data for gibbs energy, enthalpy, and entropy digitally

Where can you find the enthalpy and gibbs free energy of formation and entropy of compounds either as a data file or web api (I technically only need two since I can figure out the other one from two ...
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Given the Pair Correlation Functions for a Multi-component Fluid, is There a Simple way to Obtain the Helmholtz Free Energy?

I think it may not be possible. Given all the pair correlation functions, it seems possible to obtain the internal energy (assuming different species interact through pair-potentials (i.e. ...
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35 views

Help me understand the correlation between the equilibrium constant and delta G

I understand this up until the last two steps. How does $\text{ln}(K_{eq})$ become $2,303\text{log}(K_{eq})$ and how does $-RT*2,303$ become $-1,42$?
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Can a reaction with positive Gibbs free energy change ever occur?

If you have an endothermic reaction with a negative entropy change, is it still possible to induce the reaction in some way despite the fact that the Gibbs free energy change is positive or all ...
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66 views

Gibbs free energy or reaction enthalphy

If I conduct a reaction say, $$\ce{CaO(s) + H2O(l) \rightarrow Ca(OH)2 (aq)}$$ let us say , I want to measure the energy generated from the reaction.Will this energy I calculate equal the change in ...
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103 views

Gibbs Free Energy : What is it trying to say actually?

"Gibbs Energy is the useful work that can be extracted from the heat of a rxn or a thermodynamic process." I understand how it predicts the feasibility of a chemical rxn, considering the Entropy ...
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Heat given off from an electrochemical cell compared to mixing reactants

My confusion regarding the difference between the heat given off in a reaction that takes place in an electrochemical cell compared to in a beaker/appropriate container when the reactants are simple ...
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What value of temperature does T represent in Gibbs Free Energy Equation?

Temperature before, or after reaction? Temperature change? Or what is it?
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Why is dG=dH-TdS?

I get that $G=H-TS$ because then: $dG=dH-TdS-SdT=TdS+VdP-TdS-SdT$. Therefore, by cancelling: $dG=VdP-SdT$ which is the equations for dG. However, I cant get this result from using $dG=dH-TdS$. ...
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Why is Gibbs free energy more useful than internal energy?

$$\mathrm{d}U<T\,\mathrm{d}S-p\,\mathrm{d}V= \left(\frac{\partial U}{\partial S}\right)_{\!V}\,\mathrm{d}S +\left(\frac{\partial U}{\partial V}\right)_{\!S}\,\mathrm{d}V$$ So for a change to occur ...
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106 views

Calculating the Gibbs Free Energy of Mixing

This is a Physical Chemistry Question and comes from the Atkins Physical Chemistry book. The answers are given but I don't understand how to get to $-9.7~\mathrm{kJ}$ for the first part of the ...
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71 views

How to derive the pressure dependency for the Gibbs free energy?

$$\mathrm{d}G=\left(\frac {\partial G}{\partial p}\right)_T+\left(\frac {\partial G}{\partial T}\right)_p$$ The above is an exact differential. Firstly what does this mean physically? (I hear about ...
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How can -G/T and -A/T be thought of as 'disguised' entropies?

I understand that entropy is defined as $\mathrm{d}S=\mathrm{d}q/T$ for a reversible change but I fail to see why $-G/T$ and $-A/T$ can be thought of as 'disguised' entropies. This is a question on my ...
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How is the energy of reactants in a chemical reaction found ?

A pretty rudimentary question, but I'm reviewing the concept of energy diagrams and activation energy and I'm curious to know how chemists find the energy of reactants and of a transition state in a ...
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How to find Gibbs energy for a real gas

I'm asked to find $\Delta G$ for the isothermal compression of $N_{2(g)}$ (real gas) at $0°C$ if the gas expands from $P=1\space atm$ to $P=1000 \space atm$. The fugacity coefficients are ...
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Delta G values for Pyruvate--> Alanine vs. Oxaloacetate -> Aspartate ->Asparagine

What are the delta G values for the mammalian (human) biosynthesis of alanine from pyruvate, and for the conversion of oxaloacetate to asparagine? (assuming no particular cellular restriction or other ...
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What is the correct definition of the Gibbs free energy of activation?

Is the following correct? Gibbs free energy of activation is used in energy profiles where the stabilities of the species are expressed as changes in Gibbs energy, while the activation energy Ea ...
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Why are non-polar hydrogens neglected in protein-drug binding studies?

Why are (Non-polar) Hydrogen generally neglected in a protein-ligand (or drug) binding energy calculation? They do have charge and mass. Doesn't that affect the free energy calculation?
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Name the equation $\Delta G=\Delta G^{\circ}+RT \ln Q$

As the title states, what is the name of the equation $$\Delta G=\Delta G^{\circ}+RT \ln Q$$ My textbook does not explicitly state the name and I could not find anything on google.
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Is it possible for a reaction to have an entropy change of zero?

If the question seems rather "unscientific", be kind to accept my apology. My textbook is being highly unclear about the topic and I need to know the answer to this question before I go on with my ...
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Rate-limiting in transition state theory

Suppose an initial state $A$ can transition to either state $C$ or state $D$. Suppose further that both of these two processes are rate-limited by a transition to the same intermediate state $B$, as ...
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How is it thermodynamically possible to obtain energy from a piece of coal?

If we put a piece of coal in open air we don't get any energy of it.But if we put fire to it in open air we get energy.Explain it with help of Gibbs free energy.
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What is the difference between enthalpy of formation and Gibbs free energy of formation?

I'm having trouble (not alone, apparently) understanding the concept of Gibbs free energy, but I'm beginning to. What I still don't understand, however, is how Gibbs free energy of formation differs ...
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Proving RTln($a_i$) equal to non PV work done by system,where $a_i$ is activity

We know that chemical potential is defined as ${\mu}_i={\mu}_i^{standard}+RT\ln(a_i)$. Here $a_i$ is the activity of $i^\text{th}$ component of solution. In case of gases instead of $a_i$ it is $f_i$ ...
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What is the energy change of ethene reacting with hydrogen gas?

$\ce{CH2CH2(g) + H2(g) -> CH3CH3(g)}$ Using this table, source: http://www.kentchemistry.com/images/links/Kinetics/TB08_003.GIF ...
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Why isn't ΔG equal to zero for this equilibrium reaction?

In the reaction $\ce{E(g) <=> P(g)}$ at 25°C, equilibrium is reached when the pressure of the product is 0.100 that of the reactant. What is $\Delta G$ in joules? Using $\Delta G = \text{RT} ln ...
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Activated Complex Products/Reactants

We know that an activation complex is the temporary unstable compound formed when activation energy is reached. But what dictates whether the products are indeed going to be products or if they become ...
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Clarifications on the calculation of the $\Delta\mathrm{G}$ of a reaction

I'm trying to calculate the $\Delta\mathrm{G}$ of the following reaction. Are my calculations correct? I'm also a bit puzzled, 'cause this is a endoergonic reaction right? But the $\Delta\mathrm{G}$ ...
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how is the relation between Gibbs free energy and cell potential?

First of all what is exactly Gibbs free energy in regards to an electrochemical process? How can we visualise it? How does Gibbs free energy change in an electrochemical reaction? How is it related to ...
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Derivation of relationship between equilibrium constant and Gibbs free energy change

Why is $\Delta G=\Delta G^o+RT\ln Q?$ It feels like all online sources were written for introductory Chemistry students! Where do I find a rigorous proof of this identity? Greatly appreciate it!
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Derivation of relationship between Gibbs free energy and electrochemical cell potential

Why is $\Delta G=-nFE?$ I don't understand what the motivation is behind this definition. Was it derived or just given? The textbook provides no justification for this equation. In fact, much of ...
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Transition state and free energy

I would appreciate if someone could clarify this for me. We have products A+B combining to form C+D through the transition state X. First of all, are all reactions at least virtually reversible? Is ...
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bond energy calories

I am attempting to optimize interactions for a series of random and test molecules to a protein using docking software. The software uses QM/MMGBSA to calculate free energy in joules (yes it is not a ...
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Difference between exothermic and exergonic

In High School I learned that an exothermic reactions releases energy, while an endothermic reaction needs energy to occur. Now I learned that there is a separate, somewhat similar classification ...
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Software Bond Dissociation Energies, Bond Energy and Hybridization with Polarity

I want to calculate BDE to measure the cost of hybridization of two molecules. There are many examples of protein ligand docking on the internet but there are no examples of hybridization of ligand to ...
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Calculating bond disassociation energy and bond energy for ATP [closed]

I'd like to calculate Bond Dissociation Energy and Bond Energy for ATP to a similar molecule. What free (at least for academic use) computer programs which natively support and document BDE? If you ...
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Is the activation barrier of a reaction related to the free energy or heat of formation of its reactants?

The energy barrier for activation appears in the derivation of a bimolecular reaction through collision or transition state theory, but it seems that from looking at diagram such as this one it seems ...
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How is hydration free energy of a solute measured experimentally?

I am reading a paper (Shirts, M. R.; and Pitera, J. W. and Swope, W. C. and Pande, V. S. J. Chem. Phys. 2003, 119, 5740-5761). Near the beginning of the paper (page 5745), the authors state: ...
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Minimizing Gibbs free energy with Helmholtz free energy expressions

If I have an expression for the Helmholtz free energy (from statistical associating fluid theory for a polymer system), can I still find the Gibbs free energy minimum under constant $T,P$ conditions? ...