Free energy Definition and 277 Threads

In the equation \Delta G^{\ominus} = \Delta H^{\ominus} - T\Delta S^{\ominus} does the temperature refer to the temperature of the system, or the temperature of the surroundings? BiP

Wikipedia says : In thermodynamics, the Gibbs free energy (IUPAC recommended name: Gibbs energy or Gibbs function; also known as free enthalpy[1] to distinguish it from Helmholtz free energy) is a thermodynamic potential that measures the "useful" or process-initiating work obtainable from a...

gibbs free energy change at constant pressure is zero?? IS gibbs free energy change at constant pressure zero? ΔS = q / T. At constant pressure q = ΔH so ΔS = ΔH / T So ΔG = ΔH - ΔH/T . T = 0 I think i am wrong but where? My friend tells me that q involved in enetropy is...

Suppose we have a ligand binding to a receptor in solvent medium. I am interested to know whether there is any relation between "Binding free energy" and "Solubility". Extemely sorry if I posted my question in the wrong section. I'd be glad if anyone could help me out with this. Regards...

Does magnets posses free energy? Does the machine shown in image will run? If no...give reason... I know it seems to voilate 1st law of thermodaynamics...But why it voilates it?

Homework Statement The Helmholtz free energy of a certain system is given by F(T,V) = -\frac{VT^2}{3}. Calculate the energy U(S,V) with a Legendre transformation. Homework Equations F = U - TS S = -\left(\frac{\partial F}{\partial T}\right)_V The Attempt at a Solution We...

So, in my thermo book, it says that the gibbs free energy change of a reaction is the free energy received by the system at constant T,p and constant chemical potential when the extent of the reaction varies by one mol. The part that is confusing me is the "constant chemical...

I don't think I completely understand what Gibbs energy is, Is it the work you can get out of a system at fixed Temperature and pressure. Does anyone have another angle on it cause It seems weird to me.

I have a thought experiment I don't understand. Imagine there's a grain of salt that weighs 5 mg and it's 1mm above above a pool of water and it's on a very thing piece of flimsy material that takes about 1*10^-5 Newtons of force to break. Using Newton's 2nd law, I get the grain of salt is...

\DeltaG = -n F Emax and \DeltaG = \DeltaG\circ + RT ln(Q) When do we use the first equation and when do we use the second one?

We know that free energy is a well-defined concept in thermodynamics. How about the *consumption* of free energy? Are there well-defined criteria for saying "system X has consumed E amounts of free energy" ? That requires us to define what is a physical system, and secondly, to define...

Hi everyone, There is one major concept I am struggling with, and that is why acids dissociate more at higher temperatures. How can this be explained in terms of molecular energy levels becoming accessible at higher temperature, and the fact that the spacing between adjacent energy levels id...

Homework Statement At 699 K, DeltaG (degree)=-23.25kJ for the reaction H2(g) + I2(g) <-> 2HI(g). Calculate DeltaG for this reaction if the reagents are both supplied at 10.0 atm pressure and the product is at 1.97 pressure. Homework Equations I believe this is the relevant equation G=G(degree)...

g = u + Pv - Ts To find the partial derivative of g with respect to T at constant P, we do the following. dg = du + vdP + Pdv - Tds - sdT and du = Tds - Pdv. Therefore, dg = vdP - sdT. At constant pressure, dg = - sdT. Therefore, the partial derivative is - s. I think we could...

Homework Statement For the decomposition of Ag2O(s), what is the Gibbs free energy change at 500K (assuming delta H and delta S do not vary with temparature? delta standard Gformation: -61.0 kJ/mol delta standard Hformation: -29.7 kJ/mol Homework Equations deltaG = deltaH -...

And are reactions in particle physics reversible at all? If so, why don't we ever see Gibbs free energy used in particle physics equations?

Is the gibbs free energy of some reaction in an electrochemical cell dependent upon reactant concentration? The Nernst equation clearly states that open circuit potential is dependent upon concentration, and basic thermodynamics states that open circuit potential is directly proportional to...

Could anyone please, explain the connection between the Free Energy and the Action? I know the definitions of each but not sure about the connection. I read somewhere that the free energy is the same as the action when calculated "on-shell". What does this "on-shell" thing mean in this...

Quartz, SiO2(s), does not spontaneously decompose to silicon and oxygen at 25 degrees Celsius even though the standard entropy change of the reaction is large and positive (deltaS = +182.02 J/K). Explain why. I am confused by this one fundamentally because it seems like common sense that...

I'm teaching myself thermodynamics and I'm having trouble understanding Helmholtz and Gibbs free energy. My understanding of enthalpy (H) is pretty solid I think. I understand that enthalpy is a state variable, meaning its change tells you how much heat (Q) is absorbed or released by a system...

hi, I'm studying a system using self-consistent mean field theory. And I have obtained its free energy, which however looks a bit unusual in that it bears a steep (almost abrupt) rise across the phase transition point (see the figure). This feature brought about fierce questioning from my...

It seems to me we must pick on or the other when you get right down to it, at the moment theory and evidence suggests free energy is impossible but at the same time the universe supposedly popped into existence so that would also suggest free energy is possible or that the universe/something has...

I'm wondering about entropy, free energy and disorder. I see entropy defined along the lines of "the amount of energy within a system that is unavailable to be used for useful work". So, the energy that is available to do work, ie. the Free energy, is given by the internal energy minus the...

Thermodynamics: Gibbs free energy from this "battery" reaction? Homework Statement I'm reading my textbook and it gives an example. The dH of the reaction is -316kJ/mol so that much energy is released by the reaction itself. Additionally, the entropy of the products are higher than the...

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, Δ H = -484 KJ/mol and ΔS= -89 J/mol K? 2H2(g) + O2(g) >>> 2H2O(g) Homework Equations ΔG = ΔH - TΔS The Attempt at a...

Homework Statement I know that Gibbs free energy: G=H-TS, and therefor \frac{dG}{dT}=-S , and that dS=C_P\frac{dT}{T} Now, I am to show that more generally, dS=C_P\frac{dT}{T}-\frac{dV}{dT}dP(1) (assuming that the difference between delta and d is mostly the same (symbolwise). The hint I...

Hi guys, I'm recently working on the quasi-harmonic theory. I feel confused when i find the expression of vibrational free energy is deduced using the partion function of Boltzmann distribution, i.e., Z=Sigma{exp(-(1/2+n)*hw/kT)}. Since the phonon is boson, i tried to get the same free energy...

I found textbooks on physics (long time ago, when I was a student) where the authors said (paraphrase): "We do not assert that perpetual motion is impossible. It just hasn't been seen so far." What do the mentors and contributors say about that statement? (berkeman?)

For this problem, I'm really jst trying to figure out everything that is going on and then I can simply follow through with the derivatives once I know what I'm working with. Q: For the van der Waals gas, introduce the free energy as F = U – TS and verify that its derivatives over V and T...

When it comes to thermal/statistical mechanics, I'm a little retarded... so bear with me please. I've used the helmholtz free energy (F) dozens of times, almost as many times as I've heard and read that F is a measure of the 'useful work attainable from a closed thermodynamic system,' at...

How will the world have to change when we finally get an energy sorce better then anything we currently can think of? Let's suppose this energy sorc allows for deadlyer devices then nukes how do we cope with that? Do we even want to dare to create it if it's possible? Would we just end up...

I understand why dE=TdS-PdV ...[1] at constant temperature and pressure Also, I see that F=E-TS and therefore dF=dE-SdT-TdS ...[2] and how combining [2] and [3] gives dF=-SdT -PdV QUESTION: shouldn't [1] be expressed as dE=TdS+SdT-PdV i.e if you're going to substitute...

Homework Statement There are a problems I wasn't sure about on my test. Trying to get answers for ones I had to guess on. 1. What is the maximum [Mg] that can be achieved in an aqueous solution of Mg(OH)2 with a pH=12.50? Ksp (Mg(OH)2)=5.6e-12 2. Determine the max solubility of CaF2...

the total amount of energy able to do work is the gibbs free energy of a reaction. dG=dH-TdS according to this equation, the higher the entropy gain of a system(dS) in a reaction, the more work the system can achieve. I'm confused here. I thought entropy was the energy unable to do work?

Hey all. Our heating equipment draws air through it at 5000m^3 per hour. Lets say it's 20degC outside. The fan pulls the air through and the exhaust air is 6deg cooler. So we have scavenged that 6degC for our use. Excellent. So let's pretend there are not any system...

Hi, Homework Statement Consider a mixture of different gases with N_i molecules each (i=1...k denotes the species). For ideal gases the following relation yields: S(T,V,N_1,...N_k)=\sum_{i=1}^k S_i(T,V,N_i) a)Give explicit expressions for the entropy, the internal energy, Helmholtz free...

Hi, I've recently started studying chemistry and have being going over gibbs free energy.. I understand it is a driving force causing chemical and physical changes but during my course of reading I did have some queries stem to mind. 1) In relation to equilibrium why is it that a reaction...

Quick question: why are the standard heats of formation 0 for pure elements?

Lately I've been struggling with the idea of enthalpy and what it means conceptually, especially in its use in Gibb's free energy. There is nothing in the definition of change in enthalpy that would connect logically to spontaneity or free energy. After thinking about it for a couple days...

Hi to all! I'm new in this forum and i would like to share some thoughts with you guys! i'm 40 years old and I'm thinking on create a motor with magnetic materials which will provide me electricity for my house! i need some help with what materrials i have to buy and what dimensions i...

Hi to all! I'm new in this forum and i would like to share some thoughts with you guys! i'm 40 years old and I'm thinking on create a motor with magnetic materials which will provide me electricity for my house! i need some help with what materrials i have to buy and what dimensions i...

Hi guys, We all know that Helmholtz free energy, Gibbs free energy and Enthalpy are defined by Legendre transformation. For Enthalpy H=E+PV, I can understand it as the energy required to "displace the atmosphere" plus "creating the internal energy of system". What about Gibb free energy...

Homework Statement The Helmholtz free energy is written as: dA=-SdT-pdV-VMdH when an incompressible liquid is placed in a magnetic field H. Thus, the free energy can be written as since -pdV=0: dA=-SdT-VMdH The two heat capacities can be defined as: C_H = T (dS/dT)_H and C_M = T...

I have seen lots of Ads over the internet that promise to generate electricity from nowhere by utilizing Earth's magnetic fields or other arrangements. Some promise to increase the efficiency of household electricity use by placing their equipment in series with the main supply. Are they...

Is it true? Does this really defies a law of physics? (More output than input). or is it bluff...

228 224 4 Th --> Ra + He 90 88 2228,031015u --> 224,020186u + 4,0026033u 228,031015u - [224,020186u + 4,0026033u]= 0,0082257u 0,0082257u x 931.49 MeV = 7662157,293eV 7662157,293eV x...

Homework Statement Show that the most probable energy minimises the Helmholtz free energy. Homework Equations F=E-TS(E) where S(E) is the entropy of te system of given energy E. The Attempt at a Solution Not sure how you would 'show' is ? P(E) = 1/Z *weight funciton*exp(-beta E)

I'm having trouble understanding why in a reaction, when the free energy G of the product equal the free energy G of the reactant, the reaction is at equilibrium. Here, as my book say, the system has reached its minimum free energy. I don't really get why... Could someone explain to me...? Thanks!

A sort of free energy? Possbilble or not Hi there, Let me start off by saying that I am a College student at Penn College of Technology in Williamsport, PA and I am studying Tool making Technology and Automated Manufacturing, I'd like to refer to myself as THINKER. I've been creating my own...

Hey everyone. First let me say thanks for reading this. I am doing some practice exams to prepare for a Chemistry exam on Thursday, but I’m finding I don’t know the material very well. The problem I am having the most difficulty with right now has two parts, one relating to pressure...