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CHM-21

Electrochemical cell ΔG = −nFE

ΔG = −n F E. Electrical work of a reversible cell.

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ElectrochemistryFaradayGibbs

Governing equation

ΔG=−nFE\Delta G=-nFE

E∈[−3,3]E \in \left[-3, 3\right]

where

n
Electrons (—)
E
Cell potential (V)
\Delta G
Gibbs change (kJ/mol)

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CHM-21 · circuit
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①

Governing law — red

ΔG=−nFE\Delta G=-nFE

E∈[−3,3]E \in \left[-3, 3\right]

E=−3E = -3ΔG=578.9\Delta G = 578.9

②

Domain of the variable — blue

Emin⁡=−3,Emax⁡=3E_{\min} = -3,\quad E_{\max} = 3

E∈[−3,3]E \in \left[-3, 3\right]

E=−3E = -3E=−3E = -3

③

Response curve — green

ΔG=−nFE\Delta G=-nFE

E∈[−3,3]E \in \left[-3, 3\right]

E=−3E = -3ΔG=578.9\Delta G = 578.9

④

Rate of change — amber

dΔGdE\frac{\mathrm{d}\Delta G}{\mathrm{d}E}

E∈[−3,3]E \in \left[-3, 3\right]

E=−2.962E = -2.962ΔG′=−193\Delta G^{\prime} = -193

Lecture brief

Historical brief

Ideal-gas law, van ’t Hoff, Nernst, Michaelis–Menten and Clausius–Clapeyron are physical chemistry’s working equations of equilibrium and rate. The lab is pressure, potential and kinetics. This sheet (CHM-21 — Electrochemical cell ΔG = −nFE) is the form associated with Faraday · Gibbs. Working symbols: nn, EE →\rightarrow ΔG\Delta G. The Faraday constant F is the charge of a mole of electrons. Spontaneity is E > 0 ⇔ ΔG < 0.

Purpose

Purpose: compute ΔG\Delta G from nn, EE in Physical chemistry via ΔG=−nFE\Delta G=-nFE ΔG = −n F E. Electrical work of a reversible cell. Use it when a real physical chemistry question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given n=2.000 —n = 2.000\,\mathrm{—}, E=1.100 VE = 1.100\,\mathrm{V}, the governing relation ΔG=−nFE\Delta G=-nFE yields ΔG=−212.27 kJ/mol\Delta G = -212.27\,\mathrm{kJ/mol}. Reversible isothermal cell. Move a slider: the numbers are this situation, not a canned story.

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Inputs

Outputs

  • Gibbs change \Delta G-212.27 kJ/mol
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CHM-21 · circuit
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Narration of this film

Reversible isothermal cell.

The Faraday constant F is the charge of a mole of electrons. Spontaneity is E > 0 ⇔ ΔG < 0.

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Watch on YouTube