Gibbs Definition and 188 Threads

ΔG° is the measure of Gibbs Free energy change at 1 bar but no specified temperature and also the stoichiometric amounts depending on the equation of the chemical reaction. For example, if X ->2Y then the ΔG° would be equal to ΔG°f(2Y)-ΔG°f(X). While for ΔG it is a general term for Gibbs Free...

In reaction there is a Gibbs Free energy change. I'm still not sure what this means as in my secondary school years we just learned of one component of it which is the enthalpy change. That was simple as it just showed how much heat was released or absorbed. But with Gibbs Free energy, i don't...

Gibbs Free Energy is the appropriate potential when there is both heat exchange and mechanical work (G=E-TS+PV). On the other hand the grand potential is appropriate when there is heat exchange and chemical work (g=E-TS-μN). Is there any issue in defining a potential of the form (E-TS-μN+PV)...

I'm wondering why the Gibbs function is related to the equation of state as follows (supposedly): V=(\frac{∂G}{∂P})_T I found a thread on here that mentions this relationship, but doesn't explain it at all. Any help understanding this would be appreciated, this is my first introduction to...

Hi thanks for reading. I have 2 questions regarding the topics mentioned that I'm having trouble with. Hope you guys can help me out here :) 1) The first law is ΔU=Q+W so we can rearrange this to get ΔH=ΔU+PΔV so would this indicate that ΔH only measures the heat given out at constant...

In the expression defining Gibbs free energy, G = U - TS +pV, are T and p the temperature and pressure of the environment, or of the system itself? Or is it a requirement that the system has the same temperature and pressure as the environment for the Gibbs free energy to be defined?

I am study chapter 5 of An Introduction to Thermal Physics by Schroeder and I am having trouble understanding his explanation of the differences between enthaply, Helmholtz free energy, and Gibbs free energy. Schroeder defines enthalpy of a system as its energy plus the work needed to make...

I am familiar with the equation ΔG=ΔG°+RT ln(Q).But I can't derive it.We have to use the equation to derive nernst equation. So please help.

Homework Statement For an electrochemical cell Gibbs free energy is is given by G=-nFE Gibbs free energy for a reaction at any moment in time and standard state free energy is given by G=Go + RT lnQ Derive an expression relating standard state cell potential and equilibrium constant for...

My thermodynamics textbook says that chemical potential can take any of the following symbols: μ (condition-dependent), μ∇ (standard), μΘ (standard) (superscript plimsoll line) and μO (standard), with which one of the latter 3 being used depending on the temperature chosen to define standard...

I´m having serious problems with free gibbs energy equation. My main problem is that i don't know the meaning of TΔS that appears in free gibbs formula. I know that S is entropy and T temperature; but some books say that TΔS is energy lost or dispersal energy; energy unavailable to do work; but...

I am having some trouble fully understanding the basics and I just wanted to see if somebody would please clarify this for me. First, say you have a one component system in two phases: vapor and liquid. Gibbs' phase rule restricts the system to one independent, intensive variable that may be...

Hi,Im just beginner and I m trying to learn integrals.I m just in starting phase,but still in few tences,not details...How or why we get logarithm in gibbs free energy equation?Because of integration of this equation or due to probability and statistics laws? Thanks

Hi, As I understand, during the process of phase change from a liquid to solid (or any phase change for that matter,) the temperature of the substance remains constant as the energy being applied to the substance is used in changing phase. How does this relate to Gibbs free energy? I read that...

If this isn't the correct place to ask this, please point me to where I should. I feel there are quite a few guidelines to what can be posted and what cannot, so I hope I don't break any rules! I'm working on a problem, that deals with a superheated steam, that goes from an initial state to...

Hi there, I have to solve this problem: Use the following data to estimate the molarity of a saturated aqueous solution of ##Sr(IO_3)_2## So, I think I should use the Van't Hoff equation in some way, but I don't know how. I also have: ##\Delta_r G=\Delta G^o+RT\ln K## ##K## is the...

Hi there: When using ΔG=ΔG°+RT ln Q to calculate the energy yield of a reaction, does it matter if I use ΔG° calculated at 1°C or 25°C? Also, why are there two choices and when are they each applicable? Finally, I have also seen ΔG°' written (note the prime). What does this mean and how does...

Homework Statement Assume that ΔH° and ΔS° are independent of temperature. Calculate ΔG° for the following reaction at 533 K. 2Cu(+)(aq) ----> Cu(s) + Cu(2+)(aq) Cu(2+)(aq) enthalpy (H) of formation = 64.77 kJ mol^-1; molar entropy (S) = -99.6 J K^-1 mol^-1 Cu(s) enthalpy (H) of formation =...

Hello everyone, I am trying to understand markov random fields and how it is related to the Gibbs measure and basically trying to understand the Gibbs-MRF equivalancy. Anyway, while browsing Wikipedia documents, I was looking at the page on MRFs and when I came across the following line...

Homework Statement This is an issue I'm having with understanding a section of maths rather than a coursework question. I have a stage of the density function on the full phase space ρ(p,x); ρ(p,x) = \frac {1}{\Omega(E)} \delta (\epsilon(p,x) - E) where \epsilon(p,x) is the...

Homework Statement What constraints are imposed on the use of the Gibbs equation Tds = dh - vdP Homework Equations Tds = dh - vdP The Attempt at a Solution I seem to be stuck on this question. So far I have come up with the following constraints, but I'm not even sure if they are...

Homework Statement "By applying Gibbs' phase rule to show that for an n component system, no more than n+2 phases may coexist at equilibrium Homework Equations P+F=C+2 The Attempt at a Solution Because the question says that P = n +2 I subbed this in => n+F=C. I'd like to sub...

I'm trying to figure out if the Helmholtz & Gibbs free energy are ever used outside of chemical reactions (I suppose they could be used in nuclear reactions in a plasma as well.) It seems to me that they are not, as I can only recall using them for chemical reactions in my thermodynamics course...

Hi, seen as it's Physical Chemistry I am asking about and Physical Chemistry is essentially applied Physics I figured that it would be okay to ask here. I have an exam this tuesday, and my lecturer went over some seminar questions. He provided answers to the calculations but did not provide...

I hope this isn't deemed school related. It is something I learned in school, but I'm now trying to figure out a reaction model for my work. In the process of calculating the reaction constant, usually you first determine the Gibbs energy of formation of each species, find the difference...

First my notes discover that for an isothermal transformation; ΔW ≥ ΔF Where W is the work done and F is the Helmholtz Free Energy, F = E - TS. Then it defines the Gibbs free Energy; G = F + PV "For a system at constant temperature and pressure, G never increases"; So ΔG = ΔF...

I'm trying to learn more about Markov chains and came across the Gibbs sampler x_1{t+1} ~ p(x_1|x_2 = x_2{t},...x_n{t}) x_2{t+1} ~ p(x_2|x_1 = x_1{t+1},x_3 = x_3{t},...,x_n{t}) . . . x_i{t+1} ~ p(x_i|x_1 = x_1{t+1},...,x_(i-1) = x_(i-1){t+1},x_(i+1) = x_(i+1){t},...,x_n{t}) Supposedly...

Homework Statement Consider the following reaction: CH3OH(g) <-> CO(g)+2H2(g) Calculate ΔG for this reaction at 298 K under the following conditions: PCH3OH=0.895atm PCO=0.115atm PH2=0.200atm Homework Equations ΔG=-R*T*ln(K) where R is the gas constant 8.314 J/molK, T is 298 in...

Hey, Here is the problem: The method by which we solve is by Langrange Multipliers, and so I believe I found the derivative of f with respects to P(i) but I have two quantities I'm sure what they equal: Summations over i=1 to N : Ʃln(P(i)) and ƩE(i) Thanks for any help, S

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...

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.

For a thermodynamic process, what equations would be used to find the change in Gibbs and Helmholtz free energy when: a.)The process is adiabatic b.)The process is isothermic c.)The process is at constant volume d.)The process is at constant pressure I know ΔG=ΔH-TΔS and ΔA=ΔU-TΔS but do...

Homework Statement For the reaction N2(g) + 3H2(g) <---> 2NH3(g) I am supposed to determine the equilibrium constant at 298K and 1 bar. We have been given a table that states that for NH3(g): \Delta_{r}G^{\Theta}= -16.45 kJ/mol I know that \Delta_{r}G^{\Theta}= \Sigma v...

Homework Statement In the attached picture, I am wondering if there is an error in equation (6.34). In equation (6.33), the partial differential of G/T is taken with respect to T. In (6.34), however, the partial differential of G/T is taken with respect to 1/T and the same outcome is...

1.00 mol of perfect gas at 25 C is expanded isothermally from an initial pressure of 5.00 atm to a final pressure of 1.00 atm in two ways:(a) reversibly (b) against a constant external pressure of 1.00 atm. Calculate the values for q, w, dU, dH, dG, dSsys, dSsur, dStot for each path. (I pretty...

Homework Statement 1. Derive the Gibbs function g(T,P) for dry air. T = temp, P = pressure 2. Derive the speed of sound (c) from the Gibbs function. Plot c as a function of temp and pressure. Homework Equations c = gp*squareroot(gTT/(g^2TP - gTT*gpp) I wasn't sure how to type it in...

Please teach me this: Why specific heat near critical point equals differentiate twice Gibbs free energy with respect to temperature, but not differentiate once with respect to temperature as usually doing. Thank you very much in advance.

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 -...

So, this is not a homework problem. Merely for my own understanding. This is (or should be) relatively simple I believe. Anyway, start of with Gibbs free energy and take the derivate, we arrive at: dG = -SdT + VdP + \mu dN take the partials we can see that with respect to dP we get V...

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...

Homework Statement http://img684.imageshack.us/img684/4496/fourier.png Homework Equations http://en.wikipedia.org/wiki/Small-angle_approximation The Attempt at a Solution This is part of a larger question, I have underlined in Red the areas I am struggling with and have cut out...

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...

Homework Statement Show how the Boltzmann entropy is derived from the Gibbs entropy for systems in equilibrium. Homework Equations Gibbs entropy S= - \int \rho(p,q) (ln \rho(p,q)) dpdq where \rho(p,q) is the probability distribution Boltzmann entropy S= ln\Omega where \Omega is...

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...

I have been putting some thought into understanding Gibbs energy but I can't quite figure one thing out. Here is my dilemma: Say that someone wants to react A with B to form C, and they mix pure A with pure B. At the moment the reaction starts, there is no C in the mixture (is this...