Gibbs Definition and 200 Threads

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 You have two parts of a tank, divided by a divider. On the larger side, you have 4 mol of N2 gas and on the smaller side you have 1 mol O2 gas. Both gasses are are the same T and P. The divider is removed and the gasses mix. What is the final T and P? What is the...

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...

Homework Statement Do a qualitative sketch of a G vs T (and G vs P) graph for water at liquid, solid and gas phases at atmospheric pressure. How would the graphs differ at a pressure of 0.001 bar/slightly higher temperatures? Homework Equations None that I can think of. The Attempt at a...

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...

How does the Gibbs Phenomenon effect the choice of the kth harmonics for bandwidth selection? Basically, I have plotted a square wave using the Fourier series analysis for choosing the kth harmonics. As, I increase the kth harmonics the oscillations increase. What is the smallest harmonic i...

Hi all, I have used Metropolis-Hastings rules in a Markov Chain Monte Carlo (MCMC) algorithm for a few months now. I feel quite confident with this method and I use it frequently for fitting various model parameters to observational data. Already I feel that computational time is really...

Hi all, A few weeks ago I found http://www.sv.vt.edu/classes/ESM4714/methods/Gibbs.html" by Dr. Kriz of Virginia Tech. He describes how Gibbs envisioned a 3D U-S-V (energy-entropy-volume) surface, from which Maxwell created a sculpture. Maxwell believed the surface was of great...

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...

Homework Statement I'm having some difficulty with this question, not exactly sure how to start it. Any suggestion would help. Thanks At 2.02 atm water boils at 121 °C. Calculate the change in the Gibbs free energy when one mole of steam at 121 °C and one atm condenses to liquid water at...

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?

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...

To resolve Gibbs paradox, Gibbs himself came up the idea to treat particles as indistinguishable. Since by then QM hadn't been discovered, how did Gibbs argue that particles indistinguishable? In any classical sense, particles should be distinguishable, if Gibbs did it only to resolve the...

It occurs to me that some people create codes to maximize the entropy of a system in order to predict equilibrium concentrations. However, others minimize the Gibbs function. I understand the relationship, so why the two methods? Aren't these results always the same? Is there a practical reason...

Hi guys, I have a question regarding the Gibbs paradox. Let's say we take a container A of helium gas and place it next to another container B also containing helium gas at the same temperature and pressure. When we remove the partition (wall) between them, what happens? If we use classical...

The relation, ΔG = -RT ln(Keq) is ubiquitous. It says that for a reaction, the change in Gibbs energy is proportional to the logarithm of the equilibrium constant. But where does this come from? I've been reading through many books and haven't yet find any that derive or indicate the...

Hello - I'm having some problems understanding Gibbs energy of formation, and how it's applied to electrolysis. So, I'm hoping someone can explain what I'm doing wrong.. According to his site: http://hyperphysics.phy-astr.gsu.edu/Hbase/thermo/electrol.html (image) The change in the Gibbs...

In a book about stat. mech., I read the following relaiton for magnetic system A = G + hM where A is the Helmholtz energy, G is the Gibbs energy and h is the external magnetic field, M is the magetization. I know from thermodynamic, we have A = U - TS or A = G - PV so, hM =...

Hi all, I am a bit confused about the relation between the thermodynamic potentials and the partition function. Usually one has Z = e^{-\beta A}, \qquad A = U-TS right? Here A is the Helmoltz free energy. Now, when addressing magnetic system I see Z = e^{-\beta G} where G is...

Homework Statement Suppose you have a mole of water at 198 K. and atmospheric pressure. use the data at the bac of this book to determine what happens to its gibbs free energy if you raise the temperature to 303 Kelvins. To compensate for this change, you could increase the pressure of the...

Homework Statement The reaction is NH_{4}Cl(s)\rightarrow NH_{3}(g)+HCl(g) \Delta H^{o}=+176 kJ and \Delta G^{o}=+91.2 kJ at 298 K What is the value of \Delta G at 1000 K? Homework Equations \Delta G=\Delta H-T\Delta S The same applies if all 'deltas' are standard The Attempt at...

Homework Statement Use the definitions of Helmholtz free energy, F, and Gibbs free energy, H, together with the thermodynamic identity, to show that S = -(\frac{\partial F}{\partial T})_V and S = -(\frac{\partial F}{\partial T})_P Then use those definitions again, and the...

In canonical ensemble all energy values are permitted. The distribution of energies of system at temp T follows Gibbs Distribution. My question is simple. Why is it that all energies are permitted?? forget the mathematical derivation. How to understand it physically. Does it not take the...

Homework Statement There is a formula which says the change (delta) of volume of a mixture is equal to the partial derivative of delta G with respect to pressure at constant temperature. I don't understand how there can be a derivative and the delta used at the same time on G. I thought that...

Are the concepts of exergy and Gibbs Free Energy related? What are the differences between them? Thanks in advance for any help.

For photon gas chemical potential is zero. It is because derivate of free energy with respect to number (T, V fixed) of particles is zero in equilibrium. (free energy has minimum). I was wondering why cannot I apply this reasoning to conclude (wrong) that chemical potential is zero for any Bose...

Homework Statement CaCO3 <-> CaO + CO2 At 900K, equilibrium pressure of CO2 is 0.0423 atm. Calculate Gibbs Free energy of Reaction and K.Homework Equations delta G = -RTlnKThe Attempt at a Solution delta G = 5656.3 cal/mol K = 0.0423 I have a feeling that this is incorrect Could someone...

Hi all, I was asked something today at college. We're learning about Fourier series and we talked about the Gibbs phenomenon. The teacher asked us if we could possibly come up with a way of estimating the width of the oscillation in this phenomenon. I understand that increasing the number of...

Homework Statement Write the half-reactions and the overall reaction for the oxidation of water by F2. Determine the standard potential and DeltaGr(0). Homework Equations I can manage the half-reaction and the overall reaction should be: 2 H2O + 2 F2 = 4 HF + O2 The Attempt at a...

Hi, I'm trying to answer a question that I'm stuck on. The question is as follows: -------------------------------------------------------------- If the Gibbs free energy change (deltaG) for ATP hydrolysis in a cell is -57 kJ/mol and the free energy change for transporting a proton from...

Homework Statement Determine the change in the entropy, Helmholtz free energy, and Gibbs free energy, when a mole of ideal gas is compressed from 1atm to 100atm at 20C. The Attempt at a Solution I am not entirely convinced by my attempt below -- can anyone spot something wrong? (I thought it...

Homework Statement A. Explain the need for Gibbs Free Energy equation. B. Explain what it means when: \Delta G <0 \Delta G >0 \Delta G =0 Homework Equations \Delta G= \Delta H-T \Delta S The Attempt at a Solution A. Gibbs eqn comes from the need to calculate the entropy of...

Hey guys, I'm hung up on the Gibbs Free Energy equations. I know that ?G° is the free energy change under standard conditions (1 M, 1 atm, 25ºC), and that it is characteristic for a given reaction. I think that when a reaction is occurring under conditions that are not standard the equation...

Homework Statement Calculate the Gibbs free energy for a van der Waals gas (up to an integration constant), assuming a fixed amount of material and temperature. Homework Equations P = \frac{NkT}{V-Nb} - \frac{aN^2}{V^2} dG = -SdT + VdP + udN (where u is the chemical potential) The...

Homework Statement Consider fuel cell using methane as fuel. Reaction is CH^4 + 2O_2 -> 2H2O+CO_2 Assume room temperature and atmospheric temperature Determine values of delta H (Helmholtz) and delta G (Gibbs) for this reaction for one mole of methane. Question instructed the use of...

Gibbs energy=chem potential (solved) my thermal book gives a hand-waving argument saying the followings: firstly, Gibbs energy, defined by: G\equiv U+PV-TS is an extensive quantity (proportional to N), and also \left (\frac{\partial G}{\partial N}\right ) _{T,P}=\mu so far so good, but...

Hi I am new in thermodynamics , and I thought you can help me If it is valid dG=dW May I say dG=-Pdv P=-dG/dv? thanks in advance,Mariana P=external pressure G=Gibbs energy W=maximum work

a) Consider a system that may be unoccupied with energy zero or iccuped by one particle in either of two states, one of zer oeenrgy and one of energy epsilon. Show taht the Gibbs sum for this system is z = 1 + \lambda / \lambda\exp(-\epsilon/\tau) b) Show that the thermal average occupancy...

These are some empirical excess Gibbs energy models used to calculate activity coefficients for non-ideal liquid mixtures. I didn't find many on the web, so I thought I'll put them here for future reference All x_i refer to the mole fraction of the ith species in the solution. To calculate the...

Why must Gibbs Free Energy >0 for a reaction to occur?

I don't know where to start with this problem. I must be missing an equation or something... Q: Pb(s)+2H^{+}(aq)\rightarrow Pb^{2+}(aq)+H_2(g) \,\,\,\,\,\,\,\,E^{\degree}_{cell}=+0.126V What is the \Delta G^{\degree} in \frac{kJ}{mol} for this reaction. a) -24 b) 24 c) -12 d) 12 e) 50...

Believe it or not, but working in a cement plant led me to an interresting question in thermodynamics. The original problem is related to lumps formation in a silo containing hot cement. It involves gypsum dehydration and the reverse reaction, hemihydrate (or plaster) hydration...

in a binary two-phase system will the the chemical potential in the two phases differ?

would anyone happen to know what the expression for an isothermal change in Gibbs free energy for a liquid is when the pressure changes from pi to pf. Also an expression for when its a perfect gas? i can't seem to figure them out.. and how would they be deduced? i've come across one equation...

hey i seem to be having a lot of trouble with this type of question: Calculate the change in Gibbs energy of 35g of ethanol (mass density = 0.789g cm-3) when the pressure is increased isothermally from 1 atm to 3000 atm. in my notes i have that dG=V(Pf-Pi) and search up on the net that...

Hi all. About Gibbs' paradox (with the mixture entropy for ideal gases): Is the paradox a Thermodynamic paradox? Because what's bothering me is that in Thermodynamics, the entropy is determined up to a "constant", allegedly, \[ S_0 \] , which in my opinion is dependent of \[ N \] ...

What I have not seen in books about the Gibbs paradox is that it doesn't exist if we make the Gibbs correction at the logarithm of the Z function, not at the Z function itself, in that way: \ln Z_{i} - \ln N_{i} ! where N_{i} is the number of identical particles of class i, where there...

Hi all, hopefully someone can help me out here: I'm looking at the Gibbs' method for orbit determination, and I'm losing the conceptual picture in the vector calculations. I have no problems seeing how D and N point in the W direction (PQW coordinate system), but I'll be damned if I can...