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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Exergonic process</span></span>
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<div class="side-box-text plainlist">Look up <i><b><a href="https://en.wiktionary.org/wiki/exergonic" class="extiw external" title="wiktionary:exergonic">exergonic</a></b></i> in Wiktionary, the free dictionary.</div></div>
</div>
<p>An <b>exergonic process</b> is one which there is a positive flow of energy from the system to the surroundings. This is in contrast with an <a href="Endergonic_reaction" title="Endergonic reaction">endergonic</a> process.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> Constant pressure, constant temperature reactions are exergonic <a href="If_and_only_if" title="If and only if">if and only if</a> the <a href="Gibbs_free_energy" title="Gibbs free energy">Gibbs free energy</a> change is negative (∆<i>G</i>&nbsp;&lt;&nbsp;0). "Exergonic" (from the prefix exo-, derived for the Greek word ἔξω <i>exō</i>, "outside" and the suffix -ergonic, derived from the Greek word ἔργον <i>ergon</i>, "<a href="Work_(thermodynamics)" title="Work (thermodynamics)">work</a>") means "releasing energy in the form of work". In thermodynamics, work is defined as the energy moving from the <a href="System" title="System">system</a> (the internal region) to the <a href="Surroundings" title="Surroundings">surroundings</a> (the external region) during a given process.
</p><p>All physical and chemical systems in the universe follow the <a href="Second_law_of_thermodynamics" title="Second law of thermodynamics">second law of thermodynamics</a> and proceed in a downhill, i.e., <i>exergonic</i>, direction. Thus, left to itself, any physical or chemical system will proceed, according to the <a href="Second_law_of_thermodynamics" title="Second law of thermodynamics">second law of thermodynamics</a>, in a direction that tends to lower the <a href="Thermodynamic_free_energy" title="Thermodynamic free energy">free energy</a> of the system, and thus to expend energy in the form of work. These reactions occur spontaneously.
</p><p>A <a href="Chemical_reaction" title="Chemical reaction">chemical reaction</a> is also exergonic when spontaneous. Thus in this type of reactions the Gibbs free energy decreases. The <a href="Entropy" title="Entropy">entropy</a> is included in any change of the Gibbs free energy. This differs from an <a href="Exothermic_reaction" title="Exothermic reaction">exothermic reaction</a> or an <a href="Endothermic_reaction" class="mw-redirect" title="Endothermic reaction">endothermic reaction</a> where the entropy is not included. The Gibbs free energy is calculated with the <a href="Gibbs%E2%80%93Helmholtz_equation" title="Gibbs–Helmholtz equation">Gibbs–Helmholtz equation</a>:
</p>
<dl><dd><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \Delta G=\Delta H-T\cdot \Delta S}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ<!-- Δ --></mi>
<mi>G</mi>
<mo>=</mo>
<mi mathvariant="normal">Δ<!-- Δ --></mi>
<mi>H</mi>
<mo>−<!-- − --></mo>
<mi>T</mi>
<mo>⋅<!-- ⋅ --></mo>
<mi mathvariant="normal">Δ<!-- Δ --></mi>
<mi>S</mi>
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<annotation encoding="application/x-tex">{\displaystyle \Delta G=\Delta H-T\cdot \Delta S}</annotation>
</semantics>
</math></span><img src="./81f34b838c431f0ec9850a483a6f8a39e34dd8a8.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:20.451ex; height:2.343ex;" alt="{\displaystyle \Delta G=\Delta H-T\cdot \Delta S}" loading="lazy"></span></dd></dl>
<p>where:
</p>
<dl><dd><i>T</i> = temperature in <a href="Kelvin" title="Kelvin">kelvins</a> (K)</dd>
<dd>Δ<i>G</i> = change in the Gibbs free energy</dd>
<dd>Δ<i>S</i> = change in entropy (at 298 K) as Δ<i>S</i> = Σ{<i>S</i>(<a href="Product_(chemistry)" title="Product (chemistry)">Product</a>)} − Σ{<i>S</i>(<a href="Reagent" title="Reagent">Reagent</a>)}</dd>
<dd>Δ<i>H</i> = change in enthalpy (at 298 K) as Δ<i>H</i> = Σ{<i>H</i>(Product)} − Σ{<i>H</i>(Reagent)}</dd></dl>
<p>A chemical reaction progresses spontaneously only when the Gibbs free energy decreases, in that case the Δ<i>G</i> is negative. In exergonic reactions the Δ<i>G</i> is negative and in <a href="Endergonic" class="mw-redirect" title="Endergonic">endergonic</a> reactions the Δ<i>G</i> is positive:
</p>
<dl><dd><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \Delta _{\mathrm {R} }G<0}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi mathvariant="normal">Δ<!-- Δ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">R</mi>
</mrow>
</mrow>
</msub>
<mi>G</mi>
<mo>&lt;</mo>
<mn>0</mn>
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<annotation encoding="application/x-tex">{\displaystyle \Delta _{\mathrm {R} }G&lt;0}</annotation>
</semantics>
</math></span><img src="./ccbbfe7bb3d4eae5e02f61fecf97b9cfc03a6890.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:9.465ex; height:2.509ex;" alt="{\displaystyle \Delta _{\mathrm {R} }G<0}" loading="lazy"></span> exergon</dd>
<dd><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \Delta _{\mathrm {R} }G>0}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi mathvariant="normal">Δ<!-- Δ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">R</mi>
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</mrow>
</msub>
<mi>G</mi>
<mo>&gt;</mo>
<mn>0</mn>
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<annotation encoding="application/x-tex">{\displaystyle \Delta _{\mathrm {R} }G&gt;0}</annotation>
</semantics>
</math></span><img src="./96cf9acf4bd4dcdcd9c995bfb4fe36c12fd7f248.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:9.465ex; height:2.509ex;" alt="{\displaystyle \Delta _{\mathrm {R} }G>0}" loading="lazy"></span> endergon</dd></dl>
<p>where:
</p>
<dl><dd><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \Delta _{\mathrm {R} }G}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi mathvariant="normal">Δ<!-- Δ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">R</mi>
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<mi>G</mi>
</mstyle>
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<annotation encoding="application/x-tex">{\displaystyle \Delta _{\mathrm {R} }G}</annotation>
</semantics>
</math></span><img src="./23886af1af3818e9cdbc835617b111cb2b91e249.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:5.204ex; height:2.509ex;" alt="{\displaystyle \Delta _{\mathrm {R} }G}" loading="lazy"></span> equals the change in the Gibbs free energy after completion of a chemical reaction.</dd></dl>
<div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2></div>
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<ul><li><a href="Endergonic" class="mw-redirect" title="Endergonic">Endergonic</a></li>
<li><a href="Endergonic_reaction" title="Endergonic reaction">Endergonic reaction</a></li>
<li><a href="Exothermic_process" title="Exothermic process">Exothermic process</a></li>
<li><a href="Endothermic_process" title="Endothermic process">Endothermic process</a></li>
<li><a href="Exergonic_reaction" title="Exergonic reaction">Exergonic reaction</a></li>
<li><a href="Exothermic_reaction" title="Exothermic reaction">Exothermic reaction</a></li>
<li><a href="Endothermic_reaction" class="mw-redirect" title="Endothermic reaction">Endothermic reaction</a></li>
<li><a href="Warm-blooded" title="Warm-blooded">Endotherm</a></li>
<li><a href="Ectotherm" title="Ectotherm">Ectotherm</a></li></ul>
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<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>
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<li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><a href="International_Union_of_Pure_and_Applied_Chemistry" title="International Union of Pure and Applied Chemistry">IUPAC</a>, <i><a href="IUPAC_books" class="mw-redirect" title="IUPAC books">Compendium of Chemical Terminology</a></i>, 5th ed. (the "Gold Book") (2025). Online version: (2006–) "<a rel="nofollow" class="external text" href="https://goldbook.iupac.org/terms/view/E02262.html">exergonic (exoergic) reaction</a>". <style data-mw-deduplicate="TemplateStyles:r1238218222">
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</style><a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1351%2Fgoldbook.E02262">10.1351/goldbook.E02262</a></span>
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