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In physical chemistry, the extent of reaction is a quantity that measures the extent in which the reaction proceeds. It is usually denoted by the Greek letter ξ. The extent of a reaction has units of amount (moles). It was introduced by the Belgian scientist Théophile de Donder. ==Definition== Consider the reaction :A ⇌ B Suppose an infinitesimal amount dξ of the reactant A that changes into B. The change of the amount of A can be represented by the equation dnA = – dξ and the change of B is dnB = dξ. The extent of reaction is then defined as : where denotes the amount of the i-th reactant and is the stoichiometric number 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 ξ is the extent itself. : 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「extent of reaction」の詳細全文を読む スポンサード リンク
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