Define free energy

• العربية • Asturianu • Беларуская (тарашкевіца) • Català • Español • Esperanto • فارسی • Հայերեն • Bahasa Indonesia • Italiano • עברית • മലയാളം • Bahasa Melayu • Nederlands • 日本語 • Norsk bokmål • Norsk nynorsk • Oʻzbekcha / ўзбекча • پښتو • Polski • Português • Română • Русский • Slovenščina • Svenska • ไทย • Türkçe • 粵語 • 中文 c = • v • t • e In thermodynamic free energy is one of the The free energy is the portion of any available to perform thermodynamic work at constant temperature, i.e., work mediated by The G = H − TS, where H is the T is the S is the H = U + pV, where U is the internal energy, p is the V is the volume. G is the most useful for p and temperature T, because, in addition to subsuming any entropy change due merely to heat, a change in G also excludes the pdV work needed to "make space for additional molecules" produced by various processes. Gibbs free energy change therefore equals work not associated with system expansion or compression, at constant temperature and pressure, hence its utility to The historically earlier A = U − TS. Its change is equal to the amount of T. Thus its appellation "work content", and the designation A (from Arbeit'work'). Since it makes no reference to any quantities involved in work (such as p and V), the Helmholtz function is completely general: its decrease is the maximum amount of work which can be done by a system at constant temperature, and it can increase at most by the amount of work done on a system isothermally. T...

\( \newcommand\) • • • • • • • Free energy is a composite function that balances the influence of energy vs. entropy. To first define "free" energy, we shall examine the backgrounds of this term, what definitions carry it, and which specific definitions we, as chemists, will choose to refer to: • Fossil fuels, global warming, and the usual popular controversies in popular science have led people to cry out for the pursuit of clean and renewable "free" energy (no doubt referring to long-term monetary cost). A most valiant cause; absolutely disregard it here. Forget you even read this definition. We'll even start at listing at 1. again! • If a system is isothermal and closed, with constant pressure, it is describable by the • If a system is isothermal and closed, with constant volume, it is describable by the • Having two energies both called "free energy" is like having two brothers named Jack. More specifically, they'd be twin brothers; the Gibbs and Helmholtz Energies describe situations with equations easily confused with each other. It's no wonder the IUPAC (the International Union of Pure and Applied Chemistry) officially refers to the two as Gibbs Energy and Helmholtz Energy, respectively. This should not be a surprise, because that's what they were originally named in the first place! Just keep in mind that some outdated or unsophisticated texts might still use the pseudonyms mentioned above (guised as, say, the title of a module). Gibbs Energy The Gibbs Energy is na...

Learning Objectives By the end of this section, you will be able to: • Explain the relations between potential, free energy change, and equilibrium constants • Perform calculations involving the relations between cell potentials, free energy changes, and equilibrium • Use the Nernst equation to determine cell potentials under nonstandard conditions So far in this chapter, the relationship between the cell potential and reaction spontaneity has been described, suggesting a link to the free energy change for the reaction (see chapter on thermodynamics). The interpretation of potentials as measures of oxidant strength was presented, bringing to mind similar measures of acid-base strength as reflected in equilibrium constants (see the chapter on acid-base equilibria). This section provides a summary of the relationships between potential and the related thermodynamic properties ΔG and K. E° and ΔG° The standard free energy change of a process, Δ G°, was defined in a previous chapter as the maximum work that could be performed by a system, w max. In the case of a redox reaction taking place within a galvanic cell under standard state conditions, essentially all the work is associated with transferring the electrons from reductant-to-oxidant, w elec: Δ G ° = w elec = − n F E cell ° Δ G ° = − n F E cell ° Δ G ° = w elec = − n F E cell ° Δ G ° = − n F E cell ° where n is the number of moles of electrons transferred, F is Faraday’s constant, and E° cell...

\( \newcommand\) • • • • • • • • • • • • • • • • • • • • Learning Objectives • To understand the relationship between Gibbs free energy and work. One of the major goals of chemical thermodynamics is to establish criteria for predicting whether a particular reaction or process will occur spontaneously. We have developed one such criterion, the change in entropy of the universe: if ΔS univ> 0 for a process or a reaction, then the process will occur spontaneously as written. Conversely, if ΔS univ< 0, a process cannot occur spontaneously; if ΔS univ = 0, the system is at equilibrium. The sign of ΔS univ is a universally applicable and infallible indicator of the spontaneity of a reaction. Unfortunately, using ΔS univ requires that we calculate ΔS for both a system and its surroundings. This is not particularly useful for two reasons: we are normally much more interested in the system than in the surroundings, and it is difficult to make quantitative measurements of the surroundings (i.e., the rest of the universe). A criterion of spontaneity that is based solely on the state functions of a system would be much more convenient and is provided by a new state function: the Gibbs free energy. Gibbs Free Energy and the Direction of Spontaneous Reactions The Gibbs free energy (\(G\)), often called simply free energy, was named in honor of J. Willard Gibbs (1838–1903), an American physicist who first developed the concept. It is defined in terms of three other state functions with w...

\( \newcommand\) • • • • • • • • • • • • • • Learning Objectives • To know the relationship between free energy and the equilibrium constant. We have identified three criteria for whether a given reaction will occur spontaneously: • \(ΔS_\): Criteria for the Spontaneity of a Process as Written Spontaneous Equilibrium Nonspontaneous* *Spontaneous in the reverse direction. ΔS univ> 0 ΔS univ = 0 ΔS univ 0 Q K Because all three criteria are assessing the same thing—the spontaneity of the process—it would be most surprising indeed if they were not related. In this section, we explore the relationship between the standard free energy of reaction (\(ΔG^o\)) and the equilibrium constant (\(K\)). Free Energy and the Equilibrium Constant Because \(ΔH^o\) and \(ΔS^o\) determine the magnitude and sign of \(ΔG^o\) and also because \(K\) is a measure of the ratio of the concentrations of products to the concentrations of reactants, we should be able to express K in terms of \(ΔG^o\) and vice versa. "Free Energy", \(ΔG\) is equal to the maximum amount of work a system can perform on its surroundings while undergoing a spontaneous change. For a reversible process that does not involve external work, we can express the change in free energy in terms of volume, pressure, entropy, and temperature, thereby eliminating \(ΔH\) from the equation for \(ΔG\). The general relationship can be shown as follows (derivation not shown): \[ \Delta G = V \Delta P − S \Delta T \label\) and \(K_p\) are gr...

What does it mean to have energy? Well, think about how you feel when you wake up in the morning. If you have lots of energy, that probably means you feel awake, ready to go, and able to do what needs to be done during the day. If you have no energy (maybe because you didn’t get your eight hours of sleep), then you may not feel like getting out of bed, moving around, or doing the things you need to do. While this definition of energy is an everyday one, not a scientific one, it actually has a lot in common with the more formal definition of energy (and can give you a helpful way to remember it). Specifically, energy is defined as the ability to do work – which, for biology purposes, can be thought of as the ability to cause some kind of change. Energy can take many different forms: for instance, we’re all familiar with light, heat, and electrical energy. Here, we’ll look at some types of energy that are particularly important in biological systems, including kinetic energy (the energy of motion), potential energy (energy due to position or structure), and chemical energy (the potential energy of chemical bonds). Energy is never lost, but it can be converted from one of these forms to another. When an object is in motion, there is energy associated with that object. Why should that be the case? Moving objects are capable of causing a change, or, put differently, of doing work. For example, think of a wrecking ball. Even a slow-moving wrecking ball can do a lot of damage to ...

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The second law of thermodynamics says that the entropy of the universe always increases for a spontaneous process: Δ S universe = Δ S system + Δ S surroundings > 0 \Delta \text > 0 Δ S universe ​ = Δ S system ​ + Δ S surroundings ​ > 0 delta, start text, S, end text, start subscript, start text, u, n, i, v, e, r, s, e, end text, end subscript, equals, delta, start text, S, end text, start subscript, start text, s, y, s, t, e, m, end text, end subscript, plus, delta, start text, S, end text, start subscript, start text, s, u, r, r, o, u, n, d, i, n, g, s, end text, end subscript, is greater than, 0 • At constant temperature and pressure, the change in Gibbs free energy is defined as Δ G = Δ H − T Δ S \Delta \text G = \Delta \text H - \text\Delta \text S Δ G = Δ H − T Δ S delta, start text, G, end text, equals, delta, start text, H, end text, minus, start text, T, end text, delta, start text, S, end text . • In chemistry, a spontaneous processes is one that occurs without the addition of external energy. A spontaneous process may take place quickly or slowly, because spontaneity is not related to kinetics or reaction rate. A classic example is the process of carbon in the form of a diamond turning into graphite, which can be written as the following reaction: C ( s , diamond ) → C ( s , graphite ) \text C(s, \text ) C ( s , diamond ) → C ( s , graphite ) start text, C, end text, left parenthesis, s, comma, start text, d, i, a, m, o, n, d, end text, right parenthesis, right ...

Learning Objectives • To get an overview of Gibbs energy and its general uses in chemistry. • Understand how Gibbs energy pertains to reactions properties • Understand how Gibbs energy pertains to equilibria properties • Understand how Gibbs energy pertains to electrochemical properties Gibbs free energy, denoted \(G\), combines • constant temperature and • constant pressure. If \(ΔG\) is positive, then the reaction is nonspontaneous (i.e., an the input of external energy is necessary for the reaction to occur) and if it is negative, then it is spontaneous (occurs without external energy input). Introduction Gibbs energy was developed in the 1870’s by Josiah Willard Gibbs. He originally termed this energy as the “available energy” in a system. His paper published in 1873, “Graphical Methods in the Thermodynamics of Fluids,” outlined how his equation could predict the behavior of systems when they are combined. This quantity is the energy associated with a chemical reaction that can be used to do work, and is the sum of its enthalpy (H) and the product of the temperature and the entropy (S) of the system. This quantity is defined as follows: \[ G= H-TS \label \] where • \(U\) is internal energy (SI unit: joule) • \(P\) is pressure (SI unit: pascal) • \(V\) is volume (SI unit: \(m^3\)) • \(T\)is temperature (SI unit: kelvin) • \(S\) is entropy (SI unit: joule/kelvin) • \(H\) is the enthalpy (SI unit: joule) Gibbs Energy in Reactions Spontaneous - is a reaction that is consid...

\( \newcommand\) • • • • • • • Free energy is a composite function that balances the influence of energy vs. entropy. To first define "free" energy, we shall examine the backgrounds of this term, what definitions carry it, and which specific definitions we, as chemists, will choose to refer to: • Fossil fuels, global warming, and the usual popular controversies in popular science have led people to cry out for the pursuit of clean and renewable "free" energy (no doubt referring to long-term monetary cost). A most valiant cause; absolutely disregard it here. Forget you even read this definition. We'll even start at listing at 1. again! • If a system is isothermal and closed, with constant pressure, it is describable by the • If a system is isothermal and closed, with constant volume, it is describable by the • Having two energies both called "free energy" is like having two brothers named Jack. More specifically, they'd be twin brothers; the Gibbs and Helmholtz Energies describe situations with equations easily confused with each other. It's no wonder the IUPAC (the International Union of Pure and Applied Chemistry) officially refers to the two as Gibbs Energy and Helmholtz Energy, respectively. This should not be a surprise, because that's what they were originally named in the first place! Just keep in mind that some outdated or unsophisticated texts might still use the pseudonyms mentioned above (guised as, say, the title of a module). Gibbs Energy The Gibbs Energy is na...