Gibbs Definition and 203 Threads

Homework Statement Are the Gibbs and Boltzmann entropies always equivalent? Homework Equations $$ S=k_{B}ln\Omega $$ [Boltzmann entropy, where ##\Omega## is the number of available microstates $$ S=-k_{B}\sum_{i}p_{i} ln(p_{i}) $$ [Gibbs entropy, where ##p_{i}## is the probability of a...

It seems to me that Gibbs' Paradox (that the entropy of a classical ideal gas, calculated by phase-space volume, is not extensive) can be resolved without assuming that particles are indistinguishable. Suppose instead the opposite: that particles are distinguishable, meaning that each one can...

Hello. A known equation that is useful for calculating equilbrium constants is: ΔG° = -RT * ln(K) This is all well and good. Given a standard gibbs free energy of reaction for some given reaction, the equilibrium constant for the reaction can be found. My trouble is in which ΔG° to use. For...

Say I have an exothermic reaction, whose change in Entropy is positive. (not the most common of reactions, but it can still happen) If I increase the temperature, by La Chatlier's principle, the reaction should move to the left. However, by Gibbs free energy, if I increase the temperature, the...

So I know that things in the Universe tend to move toward a state of least potential energy. This is why forces point in the direction of decreasing potential energy, as everything is trying to minimize its potential energy. So my main question is: does Gibb's free energy basically just...

We were learning about the change in free energy in class, but I was wondering since the Gibbs free energy decreases as a system becomes more stable, is the minimum absolute free energy for a material the same for every material, or can other materials be more stable than others?

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...

Spontaneous negative entropy reactions can occur when the internal energy decrease is greater than the negative dS*T. dG=dU-dST is spontaneous if dG is negative. The moon is receiving at least 1E8 J/s from the loss of rotational energy from the Earth's water and air. A lot more rotational...

1. Surfactant molecule is made from water-loving head and grease-loving tail (Figure 1). My question: How do we measure the cross-sectional area of the alkyl chain of surfactant? Do we measure it vertically (refer to GREEN DOUBLE ARROWS of Figure 1) or horizontally (refer to RED DOUBLE ARROWS of...

1. Surfactant molecule is made from water-loving head and grease-loving tail (Figure 1). http://tinypic.com/r/2j2gdah/9 (Figure 1) My question: How do we measure the cross-sectional area of the alkyl chain of surfactant? Do we measure it vertically (refer to GREEN DOUBLE ARROWS of Figure 1) or...

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...

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...

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...

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.

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

Hello, I consider an ideal superconductor with the gibbs-energy $$ d G=-SdT + VdP - \mu_0 M V dH$$ and helmholtz energy $$ dF = -SdT -P dV + \mu_0 V H dM$$ Assuming, that in the normal state the magnetization is too small, so that G_n(H) = G_n(H=0) and at the transition point H_c the...

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...

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. However since the decomposition potential is higher doesn't it...

I am referring to the paper entitled "New Adsorption Model -Theory, Phenomena and New Concept - " which is published in J. Oleo Sci. (https://www.jstage.jst.go.jp/article/jos/64/1/64_ess14213/_article) I have question on your paper on paragraph 3 page 2 stating "The important finding is that...

In class we have been deducing the typical equations for chemical equilibrium. What bothers me was the term ##\Delta Gº## as opposed to ##\Delta G##. ##\Delta G## is fine with me because it takes into account the fact that during a reaction the multiple components find themselves in a mixture...

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.

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...

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)...

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...

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...

What is the degrees of freedom at the critical point of a 1 component system such as water. in my test I put zero because the critical point is a POINT that is fixed per substance. is there any books that can back me up? I heard that my teacher said there was 1 degree of freedom which I am...

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...

I have seen a discussion of what would happen for an ideal gas expands irreversibly and adiabatically until absolute zero degree K. The entropy change is like that: Δs=Cv ln(T2/T1)+R ln(V2/V1) It is impossible for T2 to be zero K in the equation and so it becomes one justification of the...

Hey! :o I am looking at the Gibbs Phenomenon for the function $\displaystyle{f(x)=sgn(x), x \in [-\pi, \pi]}$. The Fourier series of this function is: $$sgn(x) \sim s(x)=\sum_{k=1}^{\infty} \frac{4}{(2k-1) \pi} \sin{((2k-1)x)}$$ Since $f$ is odd, it's sufficient to look its behaviour at $[0...

Hey! :o I am looking at the Gibbs phenomenon. We want to look at the behaviour of a Fourier series of a region of discontinuity of $f$, especially we are looking at the function $f(x)=sgn(x), x \in [-\pi, \pi]$ near $0$.Since $f$ is odd, it suffices to look its behaviour at $[0, \pi]$. Why...

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

Homework Statement a) Starting from the statement that total entropy (Ssystem+Ssurr) can only increase, show that G = U - TS +pV will attain its minimum value for a system in equilibrium with a fixed pressure and temperature reservoir. b)At atmospheric pressure, a particular substance is...

Hello I am working on deriving the expression relating the equilibrium constant K to the change in Gibbs energy. This part seems to be followed okay, but here I am not following why the change in Gibbs energy of reaction is defined this way. I can see why K is defined in a way because...

Hello everyone, I am having a little difficulty understand precisely what Gibbs free energy is. I have read in my textbook that a negative change in Gibbs free energy implies that the substance under consideration will react/change spontaneously. As such, the more negative the Gibbs free...

I calculated some gibbs free energy values for a chemical reaction at 298K and 1773K both giving me negative values . the amount for the reaction at 298K is -162443J and the one at 1773K is -81147.85J. Both shows that the reaction are spontaneous and so thermodynamically the process at 298K is...

Isothermal Titration Calorimetry measures the enthalpy of (e.g.) protein binding by measuring the amount of heat that must be added/removed to a solution in order to perfectly balance the heat generated/released by the gradual introduction of a protein's binding partner. My understanding is that...

what is actually meant by gibbs free energy and what is the difference between gibbs free energy and activation energy?In an enthalpy diagram how can it be denoted(just like for activation energy is denoted by the energy difference between transition state and reactants' enthalpy)?I just search...

Does atom at the surface of a crystal have more or less energy than those in the bulk? And how does this relate to their Gibbs free energy?

This article insinuates that the physics community had forgotten Gibbs entropy long ago and has used Boltzmann entropy since. Isn't this nonsense? For me it was always clear that Boltzmann entropy is problematic...

*to moderators: i apologize about the double post, but i didn't know how to get rid of the other post and i wanted a get an answer asap and no one was answering the other post so i reposted here in the appropriate section* enthalpy is the energy available if a system with some defined volume...

***i just realized that i posted this in the wrong section; could a moderator perhaps move this thread to the classical physics section please? Sorry for the trouble*** enthalpy is the energy available if a system with some defined volume were to be annihilated and have the atmosphere...

The Gibbs paradox in statistical mechanics is usually resolved by saying that particles do not have distinct trajectories, and so are truly identical. For example, http://ocw.mit.edu/courses/physics/8-333-statistical-mechanics-i-statistical-mechanics-of-particles-fall-2007/lecture-notes/...

Homework Statement When gaseous nitrogen and hydrogen are converted to gaseous ammonia, then delta G equals: -16.64Kj/mol 3h2+ n2=2nh3 Using the s values , calculate the delta h for the formation of ammonia Homework Equations Delta s for: H2:130.6 N2:191.5 Nh3:192.5 T= 298...

A seemingly good way to understand the overshoot and decay (ringing) of a square wave on a scope is that it is the result of bandwidth limiting. In that case, the Fourier series of a square wave \Pi(t) = \frac{1}{2 \pi} \sum_{n=-\infty}^\infty \frac{\sin(n \omega/2)}{n \omega/2} \exp(i n \omega...

In statistical mechanics the macro-state of a system corresponds to a whole region in the microscopical phase-space of that same system, classically, that means that an infinity of micro-states relate to a single macro-state. Similarly, given a hamiltonian, a whole surface in the microscopical...