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| (or activation barrier) The kinetic energy that reactant molecules must have to allow them to reach the transition state so that a reaction can occur. |
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| An equation that relates the specific rate constant to activation energy and temperature. |
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| A substance that increases the rate at which a reaction occurs. It is regenerated during the course of the reaction and can then interact with more reactants to convert them into products. |
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| The study of rates and mechanisms of chemical reactions and of the factors on which they depend. |
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| A theory of reaction rates that states that effective collisions between reactant molecules must take place for reaction to occur. |
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| A collision between molecules that results in reaction; one in which molecules collide with proper orientations and with sufficient energy to react. |
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| An individual step in the mechanism by which a reaction occurs. For each elementary step, the reaction orders do match the reactant coefficients in that step. |
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| A protein that acts as a catalyst in a biological system. |
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| The time required for half of that reactant to be converted into product(s). |
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| A catalyst that exists in a different phase (solid, liquid, or gas) from the reactants; the vast majority of heterogeneous catalysts are solids. |
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| A catalyst that exists in the same phase (liquid or gas) as the reactants. |
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| An equation that relates the concentration of a reactant remaining to the time elapsed; has different mathematical forms for different orders of reaction. |
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| A method of determining the rate-law expression by carrying out a reaction with different initial concentrations and analyzing the resulting changes in initial rates. |
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| The power to which the reactant's concentration is raised in the rate-law expression. |
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| The sum of the powers to which all concentrations are raised in the rate-law expression; also called the overall order of a reaction. |
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| (also called specific rate constant) An experimentally determined proportionality constant that is different for different reactions and that, for a given reaction, changes only with temperature or the presence of a catalyst; k in the rate-law expression, rate = k[A]x[B]y. |
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| The change in concentration of a reactant or product per unit time. |
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| The slowest elementary step in a reaction mechanism; the step that limits the overall rate of reaction. |
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| (also called rate law) An equation that relates the rate of a reaction to the concentrations of the reactants and the specific rate constant; rate = k[A]x[B]y. The exponents of reactant concentrations do not necessarily match the coefficients in the overall balanced chemical equation. The rate-law expression must be determined from experimental data. |
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| The progress along the potential energy pathway from reactants to products. |
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| A species that is produced and then entirely consumed during a multistep reaction; usually short-lived. |
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| The sequence of fundamental steps by which reactants are converted into products. |
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| A reactant in an enzyme-catalyzed reaction. |
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| thermodynamically favorable (spontaneous) reaction |
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| A reaction that occurs with a net release of free energy, G; a reaction for which ?G is negative. |
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| A relatively high-energy state in which bonds in reactant molecules are partially broken and new ones are partially formed. |
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| A theory of reaction rates that states that reactants pass through high-energy transition states before forming products. |
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