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{"term":{"metadata":{"id":"05962","doi":"10.1351\/goldbook.S05962","code":"S05962","status":"current","longtitle":"IUPAC Gold Book - steady state","title":"steady state","contexts":[],"contains":"steady state approximation (treatment)","index":null,"version":"2.3.3","lastupdated":"2014-02-24"},"definitions":{"definition":[{"id":"1","text":"In a kinetic analysis of a complex reaction involving unstable intermediates in low concentration, the rate of change of each such intermediate is set equal to zero, so that the rate equation can be expressed as a function of the concentrations of chemical species present in macroscopic amounts. For example, assume that X is an unstable intermediate in the reaction sequence: [image: Not defined] [image: Not defined] Conservation of mass requires that: [A] + [X] + [D] = [A]0 which, since [A]0 is constant, implies: -d[X]\/dt = d[A]\/dt + d[D]\/dt. Since [X] is negligibly small, the rate of formation of D is essentially equal to the rate of disappearance of A, and the rate of change of [X] can be set equal to zero. Applying the steady state approximation (d[X]\/dt = 0) allows the elimination of [X] from the kinetic equations, whereupon the rate of reaction is expressed: d[D]\/dt = -d[A]\/dt = k1.k2[A][C]\/(k-1 + k2[C]) ","contexts":{"in":[],"of":[]},"chemicals":[{"type":"chemimage","title":"Not defined","file":"S05962-1.png"},{"type":"chemimage","title":"Not defined","file":"S05962-2.png"}],"links":[{"type":"goldify","url":"http:\/\/dev.goldbook.iupac.org\/terms\/view\/C01208"},{"type":"goldify","url":"http:\/\/dev.goldbook.iupac.org\/terms\/view\/U06569"},{"type":"goldify","url":"http:\/\/dev.goldbook.iupac.org\/terms\/view\/ST06775"},{"type":"goldify","url":"http:\/\/dev.goldbook.iupac.org\/terms\/view\/R05148"},{"type":"goldify","url":"http:\/\/dev.goldbook.iupac.org\/terms\/view\/E02038"},{"type":"goldify","url":"http:\/\/dev.goldbook.iupac.org\/terms\/view\/R05156"},{"type":"internal","url":"http:\/\/dev.goldbook.iupac.org\/terms\/view\/U06569"},{"type":"internal","url":"http:\/\/dev.goldbook.iupac.org\/terms\/view\/R05141"},{"type":"internal","url":"http:\/\/dev.goldbook.iupac.org\/terms\/view\/CT01038"}],"math":[{"meaning":null,"type":"equation","latex":"[\\text{A}] + [\\text{X}] + [\\text{D}] = [\\text{A}]_{0}"},{"meaning":null,"type":"quantity","latex":"[\\text{A}]_{0}"},{"meaning":"Rate of reaction","type":"equation","latex":"-\\frac{\\text{d}[\\text{X}]}{\\text{d}t} = \\frac{\\text{d}[\\text{A}]}{\\text{d}t}+\\frac{\\text{d}[\\text{D}]}{\\text{d}t} ."},{"meaning":null,"type":"quantity","latex":"[\\text{X}]"},{"meaning":null,"type":"quantity","latex":"[\\text{X}]"},{"meaning":null,"type":null,"latex":"\\frac{\\text{d}[\\text{X}]}{\\text{d}t} = 0"},{"meaning":null,"type":"quantity","latex":"[\\text{X}]"},{"meaning":null,"type":null,"latex":"\\frac{\\text{d}[\\text{D}]}{\\text{d}t} = -\\frac{\\text{d}[\\text{A}]}{\\text{d}t} = \\frac{k_{1}\\,k_{2}[\\text{A}]\\,[\\text{C}]}{k_{-1}\\,+k_{2}\\,[\\text{C}]}"},{"meaning":null,"type":"quantity","latex":"[\\text{X}]"},{"meaning":null,"type":"quantity","latex":"[\\text{A}]"},{"meaning":null,"type":"quantity","latex":"[\\text{D}]"},{"meaning":null,"type":null,"latex":"\\frac{\\text{d}[\\text{X}]}{\\text{d}t} = k_{2}\\,[\\text{X}]\\,[\\text{C}]"},{"meaning":null,"type":"quantity","latex":"[\\text{X}]"}],"sources":[]},{"id":"2","text":"In a stirred flow reactor a steady state implies a regime so that all concentrations are independent of time.","contexts":{"in":[],"of":[]},"chemicals":[],"links":[{"type":"goldify","url":"http:\/\/dev.goldbook.iupac.org\/terms\/view\/F02443"}],"math":[],"sources":[]}]},"sources":[{"doi":"10.1351\/pac199062112167","citation":"'Glossary of atmospheric chemistry terms (Recommendations 1990)' Calvert, J.G.; Pure and Applied Chemistry 1990 62(11) 2167","page":"2216"},{"doi":"10.1351\/pac199668010149","citation":"'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' Laidler, K.J.; Pure and Applied Chemistry 1996 68(1) 149","page":"187"}],"referencedin":[{"title":0,"url":"https:\/\/en.wikipedia.org\/wiki\/Steady_state_(chemistry)","source":"wikipedia"}],"links":{"html":"http:\/\/dev.goldbook.iupac.org\/terms\/view\/S05962\/html","json":"http:\/\/dev.goldbook.iupac.org\/terms\/view\/S05962\/json","xml":"http:\/\/dev.goldbook.iupac.org\/terms\/view\/S05962\/xml","plain":"http:\/\/dev.goldbook.iupac.org\/terms\/view\/S05962\/plain","pdf":"http:\/\/dev.goldbook.iupac.org\/terms\/view\/S05962\/pdf","originalpdf":"http:\/\/iupac.org\/goldbook\/S05962.pdf"},"citeas":"IUPAC. Compendium of Chemical Terminology, 2nd ed. (the \"Gold Book\"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http:\/\/goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. https:\/\/doi.org\/10.1351\/goldbook.","license":"Licensed under Creative Commons Attribution-NoDerivatives (CC-BY-ND) 4.0 International (https:\/\/creativecommons.org\/licenses\/by-nd\/4.0\/)","disclaimer":"The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.","accessed":"2019-11-19T13:08:08+00:00"}}