Name: gibbs free energy and reaction work
Uploaded: 2023-04-30T10:08:58.000Z
Duration: 1 min 5 s
Channel: JoVE

K12 Standards

Minnesota Academic Standards in Science

9-12

Chemistry

3.1.1 9C.2.2.1.1

An Introduction to Free Energy

L'energia libera di Gibbs è l'energia disponibile per un sistema per eseguire lavori a temperatura e pressione costanti. La variazione dell'energia libera, o ∆G, può essere utilizzata per prevedere la spontaneità di una reazione.
I processi spontanei aumentano l'entropia dell'universo; tuttavia, è difficile misurare questo cambiamento di entropia perché include cambiamenti nel disordine del sistema studiato e dei suoi dintorni.
Usando l'equazione per l'energia libera di Gibbs, la spontaneità può essere determinata dalla sola variazione di entalpia ed entropia del sistema.
Se il sistema rilascia calore, l'ambiente circostante assorbe il calore, il che influenza la casualità dell'ambiente circostante. Matematicamente, l'entropia dell'ambiente circostante è uguale alla variazione di entalpia negativa del sistema divisa per la temperatura.
Riorganizzando l'equazione di Gibbs si vede che il rapporto negativo tra la variazione di energia libera e la temperatura è uguale alla variazione di entropia dell'universo.

un'introduzione all'energia libera

Come possiamo confrontare l'energia che si sprigiona da una reazione con quella di un'altra reazione? Usiamo una misurazione dell'energia libera per quantificare questi trasferimenti di energia. Gli scienziati chiamano questa energia libera Energia libera di Gibbs (abbreviata con la lettera G) in onore di Josiah Willard Gibbs, lo scienziato che ha sviluppato la misurazione. Secondo la seconda legge della termodinamica, tutti i trasferimenti di energia comportano la perdita di energia in una forma inutilizzabile come il calore, con conseguente entropia. L'energia libera di Gibbs si riferisce specificamente all'energia di una reazione chimica che è disponibile dopo aver tenuto conto dell'entropia. In altre parole, l’energia libera di Gibbs è energia utilizzabile o energia disponibile per svolgere lavoro.

Ogni reazione chimica comporta una variazione di energia libera, chiamata delta G (∆G). Possiamo calcolare la variazione di energia libera per qualsiasi sistema che subisce tale cambiamento, come una reazione chimica. Per calcolare ∆G, sottrai la quantità di energia persa nell'entropia (indicata come ∆S) dalla variazione di energia totale del sistema. L'energia totale nel sistema è entalpia e la denotiamo come ∆H. La formula per il calcolo del ∆G è la seguente, dove il simbolo T si riferisce alla temperatura assoluta in Kelvin (gradi Celsius + 273):

ΔG = ΔH − TΔS

Esprimiamo la variazione di energia libera standard di una reazione chimica come una quantità di energia per mole del prodotto di reazione (in kilojoule o kilocalorie, kJ/mol o kcal/mol; 1 kJ = 0,239 kcal) in condizioni standard di pH, temperatura e pressione . Generalmente calcoliamo le condizioni standard di pH, temperatura e pressione a pH 7,0 nei sistemi biologici, 25 gradi Celsius e 100 kilopascal (pressione di 1 atm), rispettivamente. Si noti che le condizioni cellulari variano considerevolmente da queste condizioni standard, quindi i valori ∆G calcolati standard per le reazioni biologiche saranno diversi all'interno della cellula.

Questo testo è adattato da Openstax, Biologia 2e,<a href="https://openstax.org/books/biology-2e/pages/6-2-potential-kinetic-free-and-activation-energy">Section 6.2: Potential, Kinetic, Free, and Activation Energy</a> e Openstax, Chimica 2e <a href="https://openstax.org/books/chemistry-2e/pages/16-4-free-energy?query=free%20energy&target=%7B%22index%22%3A0%2C%22type%22%3A%22search%22%7D#fs-idm21370272"> Section 16.4: Free Energy.</a>

Un'introduzione all'energia libera

Come possiamo confrontare l'energia che si sprigiona da una reazione con quella di un'altra reazione? Utilizziamo una misura dell'energia libera per quantificare questa energia ...

Education

Didattica

JoVE Core

Cell Biology

Biologia cellulare

Unit 1

Unità 1

Energy and Catalysis

Energia e Catalisi

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

gibbs free energy and reaction work

Gibbs free energy describes the usable energy in a chemical reaction. It helps scientists compare how much energy different reactions release. This measurement is called Gibbs free energy, or G, after Josiah Willard Gibbs.

The second law of thermodynamics explains why not all energy stays available for work. Some energy is lost in an unusable form, such as heat, and this loss increases entropy. Gibbs free energy is the energy left after that entropy loss is taken into account.

Every chemical reaction has a change in free energy, written as delta G. Scientists can calculate delta G for any system that changes, including a chemical reaction. The equation is delta G = delta H − T delta S, where delta H is the total energy change, delta S is the energy lost to entropy, and T is the absolute temperature in Kelvin.

Standard free energy change is reported as energy per mole of product. It is usually given in kilojoules per mole or kilocalories per mole. Standard conditions use pH 7.0 in biological systems, 25 degrees Celsius, and 100 kilopascals, which is about 1 atm of pressure.

These standard values are useful for comparison, but cell conditions are not the same. Because the inside of a cell can differ a lot from standard conditions, the calculated delta G for a biological reaction can also be different inside the cell.

Gibbs Free Energy and Reaction Work

the first law of thermodynamics

Energy Changes in Cells and Matter

The first law of thermodynamics describes how energy changes form in the universe. The total amount of energy stays constant. Energy can move from one place to another or change into a different form, but it cannot be created or destroyed. These energy changes happen in everyday life. A light bulb changes electrical energy into light energy. A gas stove changes chemical energy in natural gas into heat energy. Plants also carry out a major energy transformation when they convert sunlight energy...

the second law of thermodynamics

Entropy and Spontaneous Change

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Cellular Enthalpy and Energy Changes

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Cell Energy Loss and Entropy

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an introduction to free energy

Gibbs free energy describes the usable energy in a chemical reaction. It helps scientists compare how much energy different reactions release. This measurement is called Gibbs free energy, or G, after Josiah Willard Gibbs. The second law of thermodynamics explains why not all energy stays available for work. Some energy is lost in an unusable form, such as heat, and this loss increases entropy. Gibbs free energy is the energy left after that entropy loss is taken into account. Every chemical...

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Cell Reactions That Release or Store Energy

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the equilibrium binding constant and binding strength

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Free Energy and Reaction Direction

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Cells Stay Out of Equilibrium

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Graphing Enzyme Kinetics Data

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Diffusion-Controlled Enzymes and Reaction Speed

Catalytically perfect enzymes are enzymes that speed up biochemical reactions at very high rates. The idea was first proposed by W. J. Albery and J. R. Knowles in 1976. These enzymes have catalytic efficiency values of about 10^8 to 10^9 M^-1 s^-1 and are also called diffusion-controlled enzymes because diffusion of the substrate into the active site is the only rate-limiting step. Examples of catalytically perfect enzymes include triose phosphate isomerase, fumarase, and superoxide dismutase.

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How Enzymes Change Shape to Catalyze

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key terms and concepts

Learn how Gibbs free energy measures usable energy in reactions, how delta G is calculated, and why standard conditions can differ from cell conditions.

Gibbs Free Energy and Reaction Work | JoVE K12

cell biology

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south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

High School

Energy

C-PS3-4

Physics

P-PS3-3

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9C.2.1.1.1

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Atoms participate in a chemical bond formation&#160;to acquire a completed valence-shell electron configuration similar to that of the noble gas nearest ...

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Radioactivity and Nuclear Equations

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Alpha (&#945;) decay is the ...

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Matter and Its Interactions: Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction. (P: 5, CC: 5, CI: PS1)

9C.2.2.1.2

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Transition metals are defined as those elements that have partially filled d orbitals. As shown in Figure 1, the d-block elements in groups 3&#8211;12 are ...

Predicting Reaction Outcomes

Kinetics describes the rate and path by which a reaction occurs. In contrast, thermodynamics deals with state functions and describes the properties, ...

Redox Reactions

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Matter and Its Interactions: Use the periodic table as a model to predict the relative properties of elements based on the patterns of valence electrons. (P: 2, CC: 1, CI: PS1)

9C.3.1.1.1

3 Developing possible explanations of phenomena or designing solutions to engineering problems
 3.1 Developing and using models 
  3.1.1 Students will be able to develop, revise, and use models to represent the students’ understanding of phenomena or systems as they develop questions, predictions and/or explanations, and communicate ideas to others.

Gibbs Free Energy and Reaction Work

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