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In chemistry, the law of mass action is a mathematical model that explains and predicts behaviours of solutions in dynamic equilibrium. Simply put, it states that the rate of a chemical reaction is proportional to the product of the masses of the reactants. Necessarily, this implies that for a chemical reaction mixture that is in equilibrium, the ratio between the concentration of reactants and products is constant. Two aspects are involved in the initial formulation of the law: 1) the equilibrium aspect, concerning the composition of a reaction mixture at equilibrium and 2) the kinetic aspect concerning the rate equations for elementary reactions. Both aspects stem from the research performed by Cato M. Guldberg and Peter Waage between 1864 and 1879 in which equilibrium constants were derived by using kinetic data and the rate equation which they had proposed. Guldberg and Waage also recognized that chemical equilibrium is a dynamic process in which rates of reaction for the forward and backward reactions must be equal at chemical equilibrium. In order to derive the expression of the equilibrium constant appealing to kinetics, the expression of the rate equation must be used. The expression of the rate equations has been rediscovered later independently by Jacobus Henricus van 't Hoff. The law is a statement about equilibrium and gives an expression for the equilibrium constant, a quantity characterizing chemical equilibrium. In modern chemistry this is derived using equilibrium thermodynamics. == History == Cato Maximilian Guldberg and Peter Waage, building on Claude Louis Berthollet’s ideas about reversible chemical reactions, proposed the Law of Mass Action in 1864.〔C.M. Guldberg and P. Waage,"Studies Concerning Affinity" ''C. M. Forhandlinger: Videnskabs-Selskabet i Christiana'' (1864), 35〕〔P. Waage, "Experiments for Determining the Affinity Law" ,''Forhandlinger i Videnskabs-Selskabet i Christiania'', (1864) 92.〕〔C.M. Guldberg, "Concerning the Laws of Chemical Affinity", ''C. M. Forhandlinger i Videnskabs-Selskabet i Christiania'' (1864) 111〕 These papers, in Norwegian, went largely unnoticed, as did the later publication (in French) of 1867 which contained a modified law and the experimental data on which that law was based.〔C.M. Guldberg and P. Waage, "Experiments concerning Chemical Affinity"; German translation by Abegg in ''Ostwald's Klassiker der Exacten Wissenschaften'', no. 104, Wilhelm Engleman, Leipzig, 1899, pp 10-125〕 In 1877 van 't Hoff independently came to similar conclusions,〔J.H. van 't Hoff, ''Berichte der Berliner Chem. Ges''., (1877) 10〕 but was unaware of the earlier work, which prompted Guldberg and Waage to give a fuller and further developed account of their work, in German, in 1879.〔C.M. Guldberg and P. Waage, "Concerning Chemical Affinity" ''Erdmann's Journal für Practische Chemie'', (1879), 127, 69-114. Reprinted, with comments by Abegg in ''Ostwald's Klassiker der Exacten Wissenschaften'', no. 104, Wilhelm Engleman, Leipzig, 1899, pp 126-171〕 Van 't Hoff then accepted their priority. 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「Law of mass action」の詳細全文を読む スポンサード リンク
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