Exam 2 Study Guide

Exam 2 Study Guide - Exam 2 Study Guide Chapter 16 Factors that affect reaction rate Concentration/pressure increase of concentration increases the

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Exam 2 Study Guide Chapter 16 Factors that affect reaction rate Concentration/pressure – increase of concentration increases the rate of reaction, increase of pressure increases the concentration which increases the rate of reaction Physical state – if the physical states are the same the reaction occurs faster, if solid and liquid then the more the surface area the faster the reaction Temperature – increase in temperature increases the amount of collisions between the molecules therefore the rate of reaction will increase Expressing the reaction rate Change in concentration over change in time Average vs. instantaneous vs. initial reaction rates – average rate is over a period of time, instantaneous rate is at a particular instant during a reaction, initial reaction rate is the instantaneous rate at the moment the reactants are mixed Can be expressed as ANY concentration in reaction – aA + bB yields cC + dD rate = -1/a [A]/ ∆t = -1/b ∆[B]/∆t = 1/c ∆[C]/∆t = 1/d ∆[D]/∆t Reactants negative, products positive 1/stoichiometric coefficient The rate law Typically a rate coefficient (note: not necessarily a "rate constant") times some concentrations to some powers – Rate = k[A] m [B] n Concentrations can be reactants, products, or neither (e.g., catalysts) The powers can be positive or negative, integral or fractional Reaction order (both overall and in a particular substance) – how the rate is affected by reactant concentration, add up the superscripts to get the order of the overall reaction No necessary relationship between a chemical equation and its rate law (unless it is an elementary reaction) – if it is an elementary reaction then the coefficient become the order/power Rate law can be determined by the method of initial rates – finding the k, and orders (m, n) by using data given to us R2/R1 = [A2] m [B2] n /[A1] m [B1] n Integrated rate laws (the expressions and how to "linearize") – pg. 701-2 Zeroth order – plot [A] t vs. t and you will get a straight line with slope of -k, [A] t – [A] 0 = -kt, rate=k[A] 0 =k First order – plot ln[A] t vs. t you will get a straight line with slope of -k, ln([A] t /[A] 0 ) = kt, rate=k[A] Second order – plot 1/[A] t vs. t you will get a straight line with slope of k, 1/[A] t – 1/[A] 0 = kt, rate=k[A]
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This note was uploaded on 01/08/2012 for the course CHEM 1515 taught by Professor White during the Fall '11 term at Oklahoma State.

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Exam 2 Study Guide - Exam 2 Study Guide Chapter 16 Factors that affect reaction rate Concentration/pressure increase of concentration increases the

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