.. _sphx_glr_api_gallery_thermo_equilibrium:

Reaction equilibrium
--------------------

The law of mass action, Gibbs-energy minimization, the van't Hoff plot,
and Le Chatelier's principle.


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  <div id='sg-tag-list' class='sphx-glr-tag-list'></div>


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    <div class="sphx-glr-thumbnails">

.. thumbnail-parent-div-open

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    <div class="sphx-glr-thumbcontainer" tooltip="For N_2O_4 \rightleftharpoons 2NO_2 the reaction quotient Q = x_{NO_2}^2/x_{N_2O_4} (at P = P^\circ), computed by reaction_quotient, rises monotonically with the extent of reaction. The law of mass action says the mixture stops changing where Q reaches the equilibrium constant K. Starting from different mixtures of reactant and product, the equilibrium compositions found by solve_equilibrium_composition all give the same Q = K.">

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  .. image:: /api/gallery/thermo/equilibrium/images/thumb/sphx_glr_plot_01_law_of_mass_action_thumb.png
    :alt:

  :doc:`/api/gallery/thermo/equilibrium/plot_01_law_of_mass_action`

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      <div class="sphx-glr-thumbnail-title">Guldberg and Waage's law of mass action: Q = K at equilibrium</div>
    </div>


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    <div class="sphx-glr-thumbcontainer" tooltip="Gibbs showed that at fixed temperature and pressure a system reaches equilibrium at the minimum of its total Gibbs energy G = \sum_i n_i\mu_i. For N_2O_4 \rightleftharpoons 2NO_2 this example plots G(\xi) from gibbs_energy_of_mixture at several temperatures and marks the composition returned by solve_equilibrium_composition, which sits at each minimum. The slope dG/d\xi = \sum_i\nu_i\mu_i (the reaction Gibbs energy) crosses zero there.">

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  .. image:: /api/gallery/thermo/equilibrium/images/thumb/sphx_glr_plot_02_gibbs_energy_minimization_thumb.png
    :alt:

  :doc:`/api/gallery/thermo/equilibrium/plot_02_gibbs_energy_minimization`

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      <div class="sphx-glr-thumbnail-title">Gibbs's equilibrium criterion: minimum total Gibbs energy</div>
    </div>


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    <div class="sphx-glr-thumbcontainer" tooltip="van&#x27;t Hoff&#x27;s equation d\ln K/dT = \Delta H^\circ/(RT^2) makes \ln K a straight line in 1/T with slope -\Delta H^\circ/R and intercept \Delta S^\circ/R. This example generates noisy equilibrium constants for N_2O_4 \rightleftharpoons 2NO_2 from van_t_hoff_equilibrium_constant and recovers the reaction enthalpy and entropy with fit_van_t_hoff.">

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  .. image:: /api/gallery/thermo/equilibrium/images/thumb/sphx_glr_plot_03_van_t_hoff_plot_thumb.png
    :alt:

  :doc:`/api/gallery/thermo/equilibrium/plot_03_van_t_hoff_plot`

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      <div class="sphx-glr-thumbnail-title">The van't Hoff plot: ln K against 1/T</div>
    </div>


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    <div class="sphx-glr-thumbcontainer" tooltip="Two disturbances of N_2O_4 \rightleftharpoons 2NO_2, an endothermic reaction that increases the number of gas molecules:">

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  .. image:: /api/gallery/thermo/equilibrium/images/thumb/sphx_glr_plot_04_le_chatelier_thumb.png
    :alt:

  :doc:`/api/gallery/thermo/equilibrium/plot_04_le_chatelier`

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      <div class="sphx-glr-thumbnail-title">Le Chatelier's principle: equilibrium shifts that oppose a disturbance</div>
    </div>


.. thumbnail-parent-div-close

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    </div>


.. toctree::
   :hidden:

   /api/gallery/thermo/equilibrium/plot_01_law_of_mass_action
   /api/gallery/thermo/equilibrium/plot_02_gibbs_energy_minimization
   /api/gallery/thermo/equilibrium/plot_03_van_t_hoff_plot
   /api/gallery/thermo/equilibrium/plot_04_le_chatelier