Free energy Definition and 277 Threads

If you had a generator in a vacuum with a magnetically levitated rotor and power was drawn from the system by induction, use your imagination on the design of the device, but my question is: Where are the flaws in this concept? (Since perpetual machines are theoretically impossible). In other...

I am not able to understand the mathematical expression of "change in Gibbs free energy", For a chemical reaction occurring at constant temperature and constant pressure, (ΔS)total = (ΔS)system + (ΔS)surrounding Considering that reaction is exothermic, ΔH be the heat supplied by system to...

CONSTRUCTION: -In the following figure a metal plate is immersed in a Trough of salt water, the wire hooked to plate is attached to a choke coil and the other end of choke coil is Grounded deep inside soil. -A...

Homework Statement My questions are based on a graph. I am trying to figure out the standard ΔH change for the graphed reaction and the standard entropy change. (1) What is the standard enthalpy change for the graphed reaction? (A) -31 KJ/mol (B) 0 (C) +12 KJ/mol (D) +11 KJ/mol (2) What is...

Homework Statement We have a Gibbs Free Energy function G=G(P, T, N1, N2) I am not writing the whole function because I just want a push in the right direction. Find expressions for the entropy, volume, internal energy, enthalpy and chemical potential. Homework Equations Maxwell Relations...

Homework Statement [/B] The density of nitrogen molecules is larger at a sea level than at a higher elevation. Assuming thermal equilibrium, what is the altitude dependence of the (Helmholtz)free energy per particle? Homework Equations F=U-TS, not sure if anything else is relevant The Attempt...

Hello, I get that ΔG measures the spontaneity/capacity of a system to do non-mechanical work, and that if: ΔG>0, the reaction is not spontaneous ΔG<0, the reaction is spontaneous ΔG=0, the reaction is at equilibrium So why is Gibbs free energy zero for phase changes at constant temperature and...

Homework Statement Homework Equations Maxwell relations The Attempt at a Solution I have an attempt at a solution, but I am not sure if I can replace the integral of dT in the helmholtz equation by the T I found using the internal energy. Does this make sense? Thanks

Hi everybody! Lately I tried to overcome some problems with understanding thermodynamics laws, and unfortunately I couldn't find anything about my question:nb) and I really hope someone can help me here... My question is: This version of Gibbs formula dG= VdP-SdT, can be applied to any close...

Hello, Gibbs free energy describes the maximum of useful work that can be done by a chemical reaction. My question is(Sorry I am not into chemistry and biochemistry) : during a chemical reaction that creates ATP, we say that ATP stores energy between its chemical bonds . For exemple this is the...

Hello, The Gibbs free energy is the maximum amount of non-expansion work that can be extracted from a closed system; this maximum can be attained only in a completely reversible process. This maximum work is equal to H-TS. My question is this TS energy is what kind of energy? and from where it...

Homework Statement Show that (∂(βA)/∂β)N,V = E, where A = E - TS is the Helmholtz Free Energy and E is the Internal Energy. Homework Equations A = E - TS dE = TdS - pdV + ΣUidni β = 1 / (kBT) The Attempt at a Solution (∂(βA)/∂β)N,V = (∂/∂β) * (βE - βTS) (∂(βA)/∂β)N,V = (∂/∂β) * (βE -...

What is the difference between 1) ΔG°' and ΔG° and 2) ΔG°' and ΔG ? ΔG° I think it is the gibbs free energy at standard state means at room temperature 1 atm pressure.

I'm wondering if there's a simple relation between the specific heat capacity (at constant chemical potential) and the Helmholtz Free Energy? I can't seem to find a relation in the literature between these three quantities, specifically.

Hello everyone, I'm reading some basics of chemistry thermodynamics, and it's hard for me to figure out what is the actual meaning of free energy. could someone please help clarifying this giving specify, real life examples, like applications in mechanical engineering. Thanks

ΔG=ΔH-TΔSsystem and ΔSsystem=qp/T and isn't qp=ΔH? Which means ΔG=0 always which is obviously wrong. But the derivation for Gibbs Free Energy is based on qsurrounding=-qsystem so shouldn't the term be equals to 0?

ΔG=ΔG°+RTlnQ are for reactions that are not under standard conditions. What does it mean under non-standard conditions for the ΔG? And what is the Q in this case? Is it Qp where it is based on the partial pressure of the gas or Qc which is based on the concentration? Thanks

The decomposition potential is always higher than the theoretically determined potential by thermodynamics. E=η+Eeq where E is the decomposition potential, η is the overpotential and Eeq is the theoretically determined potential. And ΔG=-nFE and if we were to substitute the decomposition...

Hi All, reading a paper by Langer (Theory of the Condensation Point, Annals of Physics 41, 108-157, 1967), I came across an analytical continuation technique which I do not understand (would like to upload the paper PDF but I am not so sure this is allowed). Essentially, he deals with the...

Homework Statement Show how a Legendre transformation is used to obtain the Helmholtz free energy A(T,V) from the internal energy and derive the general expression for the differential of A. Homework Equations Internal Energy is a function of Entropy and Volume. U Ξ (S, V) A Ξ (T,V) A = U...

I am not a physicist but I do have a question, is it really possible to have zero point energy? Is the free energy related to Tesla the same thing as dark energy? When you are taught physics in college are you taught something like that? (planning to start physics as a career by next year) and I...

Homework Statement Consider the Landau free energy ##\mathcal{L}=-hm+r_1 t m^2+Cm^3+s_0 m^4## with an additional ##m^3## term. We consider zero magnetic field case ##h=0## and ##s_0>0##. a.) Please show that there are two critical temperatures ##t*## and ##t_1##. When ##t<t*##, a second...

Consider an Ising model system where the total energy is ##E = −J \sum_{<ij>} S_iS_j ##, ##S_i = \pm 1## and ##< ij >## implies sum over nearest neighbours. For ##J < 0## the ground state of this system at ##T = 0## is antiferromagnetic. (All adjacent spins misaligned so net magnetisation zero...

Homework Statement The total energy of the Ising model is ##E = −J \sum_{<ij>} S_iS_j ##, where ##S_i = \pm 1## and ##< ij >## implies sum over nearest neighbours. For ##J < 0## explain why the ground state of this system at ##T = 0## is antiferromagnetic. Let ##m_{1,2}## be the magnetisations...

Homework Statement What is the standard Gibbs free energy of formation of water vapor at 25 C if for the reaction shown below under standard conditions, ΔH = -484 kJ/mol and ΔS=-89 J/mol K? 2H2 + Os→2H2O Homework Equations ΔG = ΔH-TΔS The Attempt at a Solution Usually I can do these problems...

I posted this earlier, but I just realized it might have been in the wrong section. Sorry Okay, so consider you have system in which ΔG<0 and ΔS>0. Using Gibbs free energy (ΔG=ΔH-TΔS), you'll know that it will always be negative. As the temperature increases, it will actually become more and...

Homework Statement Can anyone explain to me the gibbs free energy curve? Homework EquationsThe Attempt at a Solution [/B] What is the domain of the curve and how should I interpret it?Thanks.

Hello everybody :D My question is: given the distribution of the canonical ensemble, how do we get the helmoltz free energy? I think we can't use A = U-TS because we don't know how to write S. So what's the solution? Thanks

When reading some material concerning Ginzburg-Landau theory of superconductors, I got the following sentence: The appropriate thermodynamic potential for describing a superconductor in an applied magnetic field is the Gibbs free energy ##G## (natural variable ##H##) and not the Helmholtz free...

Homework Statement The standard free energy of activation of a reaction A is 83.7 kJ/mol at 298K. Reaction B is 10 million times faster at the same temperature. The products of each reaction are 10 kJ/mol more stable than the reactants. (a) What is the standard free energy of activation of...

I'm currently taking a Biophysics lecture. There's a vast usage of the terms Enthalpy and Gibbs Free Energy. I understood that most of the time, we're dealing with the Gibbs Free Energy, because our experiment is at constant Temperature (e.g. room temperature) and constant Pressure (e.g. 1 atm)...

Homework Statement Show that the free energy, F=SUM(E_i*p_i)+T*SUM(p_i*ln(p_i)) is minimal when p_i=e^(-E_i/T)/SUM(e^(-E_i/T)) Where E is energy, T is temperature Homework Equations Nothing really The Attempt at a Solution So if I just try and find the derivative of the force I arrive at...

what's the relation of the grand potential J=F-\mu N and total Helmholtz free energy of "system and particle environment" F^{tot}? In K. Sekimoto's book "Stochastic Energetics" P182, P310 and P311 (see screenshots in the link): Does it mean the followings:J=lim[F_{tot}-\mu N_{tot}]...

When you get the equation for the Gibbs free energy, why do you multiply -T? Can't you multiply just T? I thought about this and came up with an answer of my own, which goes like 'Because its Gibbs 'Free' Energy, when you have that free energy ( \Delta G >0) you have the energy to do...

Hello PF! Consider the free expansion of an ideal gas. The process occurs at constant temperature, therefore, ΔU = 0, Q = 0, and W = 0. Suppose we are given the initial and final pressures of the gas, and we calculate ΔG = nRT ln(P2/P1). As P2 < P1, ΔG < 0. This is intuitive, as a free expansion...

Homework Statement For a certain reaction, ΔG = 13580 + 16.1 T log10(T) - 72.59 T. Find ΔS and ΔH for the reaction at 298.15 K. Homework Equations ΔG = ΔH - TΔS \left[\frac{\partial (\Delta G)}{\partial T} \right]_P = - \Delta S The Attempt at a Solution For the sake of this thread's length I...

Homework Statement Derive an equation for the change in free energy, ΔGmixing, when ideal gases with the same temperature and pressure, are mixed. Homework Equations ΔGmixing = nRT∑(xi)ln(xi) (∂/∂T(G/T))p = -H/(TxT) The Attempt at a Solution Pi = xiPi* μi = Gi,m μ = (∂G/∂n) at constant T...

A moving magnetic field will produce current in a wire. The Earth's magnet field goes beyond the moon. Does that mean bases on the moon could somehow get free energy from a coil setup as it's effectively perpetually moving through Earth's magnetic field?

I know that gibbs free energy for say a body will be equal to = Gibbs free standard energy at 1M and Ph7(-rtlnkeq) (Where k is the concentration of product/ concentration of reactant at equilibrium)+rtlnk. How can we use the standard gibbs free for irreversible spontaneous processes? Is it...

And did he have patent/s for it... I understand that their are a lot of hoaxes and unsourced information out there so I want to know if there is some truth to the claim. I understand that energy can not be created or destroyed but what free energy is referring to is energy that is released...

Is it possible to generate energy from the Earth's rotation? Imagine a Foucault Pendulum attached to a dynamo shaft? http://www.google.com/patents/US8299636

Hello, Does this concept of "Free energy principle ( https://en.wikipedia.org/wiki/Bayesian_approaches_to_brain_function#Free_energy )", developed by Karl J. Friston, showed its relevance ? ie is it a fruitful concept in the field of neuroscience and in biology ? Patrick

1. I have a question regarding the equation ΔG° = -RT lnK. When solving for the equilibrium constant K, what is the relationship between the vapor pressure of each molecular compound in a reaction? ΔG° = Free energy change R = Universal gas constant T = Temperature K = equilibrium...

[SIZE="4"]Definition/Summary Free energy is energy available for doing work. Free energy as an independent concept does not really make any sense unless conditions are specified under which the work is to be done, for example: Helmholtz free energy (or Helmholtz energy) A\ =\ U\ - TS is...

Hello, I am working on non linear fluid dynamics with my professor. We are trying to model multiphase flows of immiscible fluids. And my professor today asked me to look up works on 'free energy flows', but I cannot find anything on the internet that I can use, let alone understand. Can someone...

I build simple electronic like this picture...

Hi. I have two questions: 1) Is -ΔG the amount of useful work a system can do while the pressure and temperature of the surroundings are constant? 2) Is exergy = -ΔG only if the pressure and temperature of the system and surroundings is constant? thanks

In euclidean quantum field theory, the imaginary part of the free energy, defined as the logaritm of the partition function, is it connected to the decay rate?

I have a question that has puzzled me during the last couple of days. Suppose that there is a system (e.g. a small box filled with gas) that is connected to a heat bath (much larger than the system) at a constant temperature T. The studied system and the heat bath are thought to be isolated from...

This question came to mind when studying voltaic cells. In voltaic cells, for some ions (Cu2+ for example), both oxidation and reduction are possible. Given both possiblities, how do we determine which reaction will take place? I first thought that comparing the signage in voltage of both...