Free energy Definition and 277 Threads

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...

Okay so I'm confused. In my book it says that ksp for Ca(OH)2 = 6.5E-6 and \Delta G=-898.5 yet when I use the equation \Delta G=-RTln(Ksp) the value I get is 29.59KJ/mol. I used R=8.314 and T=298K. What's up with that? Thanks.

I have this strange feeling, the solution is almost ready, I believe we are already entering the age of Free Energy. But no, it won't happen overnight. If I may ask, what source of energy exists anywhere in the world? Constant and is always available, completely safe and doesn't emit harmful...

\Delta G = \Delta H - T \Delta S I don't understand this equation satisfactorily. I have learned so far that endothermic reaction having a positive \Delta S_{system} is spontaneous at higher temperature because T\Delta S out-compete the enthalpy term and make the free energy change...

Hi everyone, Question In metals, for homogeneous nucleation, activation free energy required for the formation of a stable nucleus are different when the nucleus are considered as a cube and considered as a sphere and the relation between them is energy for cube is almost double of the...

Homework Statement Hi all. Lets take a look at the Helmholtz free energy. It is defined as the amount of energy one has to put into create a system once the spontaneous energy transfer to the system from the environment is accounted for. Now let's look at it once we have created the...

Does anyone know of a clean proof that a reaction will occur at constant temperature if the change in Helmholtz free energy is negative, or at constant temperature and pressure if the change in Gibbs free energy is negative? The only `proofs' I've found rely on the fact that the entropy...

Dear all, I'm coding the calculation of the free energy of an SiO2 crystal structure Using a 2-body Buckingham potential. I'm attempting to use the method of Frenkel and Ladd which consist in transform your solid reversibly into an Einstein crystal. I've read the excellent book...

The ever elusive "free energy" device... Hello. Let me begin by stating that I have no formal physics/science training, and am not here to wear a tin foil hat, close my eyes and claim that I've solved the worlds problems. That being said... I have a theory, and I'd like to be told why it...

If one has a diatomic molecule with energy levels \epsilon_l = \frac{h^2 l(l+1)}{2I} l = 0,1,2,3,4,5... if the degneracy is given by g_l = (2l+1) How does one show that the Helmholtz free energy at low temperature (h^2/Ikt large) is given by F = -3kT e^{-h^2 / IkT} + ...

What is the reasoning behind defining the helmholtz free energy as F = -kT ln Z? I always wanted to know why it was just defined as the above. Is it as a form of convenience because the macroscopic theromodynamic observables of a system at constant temperature (ie the canonical ensemble) are...

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

free energy?? water disasotiates to H+ and 0H- if you could take the dissasociated ions away, and combine them how much energy could you get out? In the liquid remaining, more would dissosciate, and the process could be continued. Where does this energy come from - it sounds like free...

I have a question about protein folding. I have heard that there is a free energy barrier to overcome in going from the unfolded (ensemble) to folded states, and that this barrier is largely entropic -- i.e., as the (idealized, general) protein starts to fold, it loses more in entropy than it...

Helmholtz free energy decreases... Hello... I'm having trouble getting my head around something. I'm not exactly sure what is meant by the Helmholtz free energy (F) decreasing in a system that's in thermal equilibrium with it's environment. Under what circumstances does it decrease...

[SOLVED] free energy of formation Homework Statement Consider the reaction 2NH3(g) --> N2(g) + 3H2(g) If the standard molar free energy of formation of NH3(g) at 298 K is –16.45 kJ·mol–1, calculate the equilibrium constant for this reaction at 298 K. The correct answer is 1.71E-6...

Homework Statement The neutnral carbon atom has a 9-fold degeerate ground level and a 5-fold degenerate excited level at an energy 0.82 eV above the ground level. Spectroscopic measurements of a certain star show that 10% of the neutral carbon atoms are in the excited level, and that the...

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...

Hello, I am working on some calculations and need to find the surface free energy value of amorphous SiO2 and MgO. will anyone please tell me where I can find those values? Thanks a lot

Thought you guys might find this article interesting and that maybe it would spark some conversation. What are your thoughts on this? I think it's pretty incredible, but there has to be something that limits the process so that he can't take power away from the motor completely. Video...

It's thermo.. so I just posted it in the physics forums but.. a free energy diagram is supposed to represent G right? We normally conclude whether a rxn is endo/exothermic depending on whether the product is at a "lower" or higher energy than the reactants just by looking at the diagram...

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...

I have read in several places that superconducting materials are the closest phenomenon to perpetual motion known to science (constant flowing electrons within a circuit without resistance). The problem is that the energy required to cool the inducting material to its superconducting temperature...

Calculate ΔG for the dilution of aqueous HCl from 0.89 M to 0.253 M at 25°C. THis was a question I had to do some time earlier for one of my assignments. I got some help from a classmate and he said THE FOLLOWING: "H+ and Cl- are equimolar so you have to put them to the power of two...

2NH3(g) + 3O2(g) + 2CH4(g) http://a1.educog.com/res/sfu/batchelo/Gallery/thermodynamics/Tcat.rxn.arrow.gif 2HCN(g) + 6H2O(g) ΔH° for this equation -939.8 kJ ΔS° for this equation 165 J/K ΔG° at 232°C, for this equation -1023.1 kJ Are the following statements about this process...

I realize that this is a chem prob, but I'm stuck with what I thought was a straightforward problem while studying for my physical chemistry exam. Homework Statement The standard molar enthalpy of combustion of solid phenol (C6H5OH) is -3054 kJ/mol at 298k and it's standard molar entropy...

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...

The total (free) energy for single molecule. The better if there is a free energy-volume(pressure) function. I searched the APS and JCP,JPC journals,still cann't find it. Thanks for your time.

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...

Thermodynamics question: How much work can be obtained from sunlight? It seems like a solar panel within the sun would not continuously generate electricity (else it could purely convert heat to work) but instead would emit as much black-body radiation as it absorbs. Back here the light is...

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...

Hello, We are two students trying to build a small scale Tesla Tower (http://en.wikipedia.org/wiki/Wardenclyffe_Tower) that perhaps would transmit electrical energy wirelessly through a house. But first, before we start building this, we are starting on a small scale electrical energy...

Homework Statement Calculate the equilibrium constant for the reaction forming nitric oxide at room temperature, 25C. G= 1.73x10^5 J/mol, H = 180.5KJ/mol an S = 24.8J/(mol.K) Homework Equations ln K = -G/RT The Attempt at a Solution I subsiuted ln K = (-1.73x10^5) /...

I have a tube 1 m long and 1 m wide with an ideal fluid inside with a pressure of 1 bar. I conect that tube of 1*1m with another tube of 1m long and 0.5m wide and this connected to another tube of 1 m and 0.25 m wide and so on So i have a tube in which every 1 m of length the wideness of...

Hello, could someone expalin me the concept of free energy. Please.

I'm not sure whether this belongs in the chemistry section, but since it concerns free energy, I decided to post it here. My chemistry text, Zumdhal, says (without proof, I am self-studying a first year college-level chem course) that \Delta G = \Delta G^{\circ} + RTln(Q), where Q is the...

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

The relationship between free energy and the equilibrium constant is Go = -RT ln K By measuring the pH at various temperatures, the Kb for NH3(aq) was found to be temperature dependent, yielding the following values: temperature (K) Kb 283 1.34 X 10-5 293 1.42 X 10-5 303 1.50 X...

Couldn't help noticing this... :smile: :smile:

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

A friend of mine asked me where the energy comes from in this setup: Imagine a fan/windmill inside a box. The fan is only allowed 2 turn clockwise and is connected to an axel which exits the box. The atmosphere will keep the air inside the box at, well, atmospheric temperateure. Every so...

could this be future free energy? http://www.boinc.ch/~sleepsleep/blend/fe.png" when the bowling ball drops down from left (air) tube, we would use its energy (due to gravity) to pull another bowling ball in (water) tube. if u see the graphic, there is a "air" pad that to make the...

Forgive me if this sounds ignorant; I have no professional knowledge of physics. But I've wondered if it is possible to obtain free energy from gravity in this manner: I remember seeing a documentary on an attempt to build the world's tallest building. Apparently, it could only be built so tall...

Then check out this Irish company... http://www.steorn.net/frontpage/default.aspx http://news.yahoo.com/s/afp/20060818/bs_afp/irelandscienceenergy

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...

Hi to everyone at the forum. I've attached the question in word format so you can see it properly but it is basically this: ----- The Gibb's Free Energy is: G(T, P, N) = U - TS + PV Where N is the number of particles. (Only one type of particle is present). Explain why the...

Calculate the gibbs free energy for a reaction which has a standard enthalpy = -196kJ/mol and standard entropy = 151 J/K mol at 32C. G = -196 KJ/MOL -[-305.15 K*0.15] = -242KJ Thank you.

Are my final values correct? 1. Determine the free energy change associated with the formation of methanol from carbon monoxide and hydrogen gas if the partial pressure of CO is 1.0700 atm, H2 is 2.2800 atm, and CH3OH is 0.0600 atm at 298K. The standard free energy of formation for methanol...