Extent of Reaction
Get Extent of Reaction essential facts below. View Videos or join the Extent of Reaction discussion. Add Extent of Reaction to your PopFlock.com topic list for future reference or share this resource on social media.
Extent of Reaction

In physical chemistry, extent of reaction is a quantity that measures the extent in which the reaction proceeds. It is usually denoted by the Greek letter ?. The extent of a reaction has units of amount (moles). It was introduced by the Belgian scientist Théophile de Donder.


Consider the reaction

A ? B

Suppose an infinitesimal amount d? of the reactant A changes into B. The change of the amount of A can be represented by the equation dnA = - d? and the change of B is dnB = d?.[1]

The extent of reaction is then defined as[2][3]

where denotes the amount of the i-th reactant and is the stoichiometric coefficient (or stoichiometric number using IUPAC nomenclature[4]) of the i-th reactant. In other words, it is the amount of substance that is being changed in an equilibrium reaction. Considering finite changes instead of infinitesimal changes, one can write the equation for the extent of a reaction as

The extent of a reaction is defined as zero at the beginning of the reaction. Thus the change of ? is the extent itself.


The relation between the change in Gibbs reaction energy and Gibbs energy can be defined as the slope of the Gibbs energy plotted against the extent of reaction at constant pressure and temperature.[1]

Analogously, the relation between the change in reaction enthalpy and enthalpy can be defined.[5]


The extent of reaction is a useful quantity in computations with equilibrium reactions. Consider the reaction

2A ? B + 3 C

where the initial amounts are , and the equilibrium amount of A is 0.5 mol. We can calculate the extent of reaction from its definition

Do not forget that the stoichiometric number of reactants is negative. Now when we know the extent, we can rearrange the equation and calculate the equilibrium amounts of B and C.


  1. ^ a b Atkins, Peter; de Paula, Julio (2006). Physical chemistry (8 ed.). p. 201. ISBN 978-0-7167-8759-4.
  2. ^ Lisý, Ján Mikulá?; Valko, Ladislav (1979). Príklady a úlohy z fyzikálnej chémie. p. 593.
  3. ^ Ulický, Ladislav (1983). Chemický náu?ný slovník. p. 313.
  4. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "stoichiometric number, ?". doi:10.1351/goldbook.S06025
  5. ^ Lisý, Ján Mikulá?; Valko, Ladislav (1979). Príklady a úlohy z fyzikálnej chémie. p. 593.

  This article uses material from the Wikipedia page available here. It is released under the Creative Commons Attribution-Share-Alike License 3.0.



Music Scenes