CHAPT14b F10

CHAPT14b F10 - Chapter 14 CHEMICAL KINETICS CHEMICAL...

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Chapter 14 CHEMICAL KINETICS CHEMICAL KINETICS : area of chemistry that deals with reaction rates FACTORS AFFECTING THE RATE OF CHEMICAL REACTIONS Nature of the reactant : Reactivity, weak bonds, strong bonds, family, etc Contact of reactants: Homogeneous reactions: all species are in the same phase Heterogeneous reactions: species present in different phases Surface area:  a larger surface area will increase the reaction rate Concentration of reactants : higher concentration will increase the reaction rate Temperature:  Increasing the temperature increases the kinetic energy, increasing the  reaction rate  Catalyst:  Addition of a catalyst speeds up the rate of reaction… more later    REACTION RATE  is the increase in molar concentration of product over time OR the decrease  in molar concentration of reactant per unit time - usual unit M/s Determination of reaction rate.  Board discussion. (See Table 14.1 and Figure 14.4 on  page 577.) The reaction is    C 4 H 9 Cl  (aq)  + H 2 O (l)  ---> C 4 H 9 OH  (aq)  + HCl (aq) Over time the concentration of C 4 H 9 Cl will decrease and the concentration of C 4 H 9 OH will  increase. Average rate for the disappearance of C 4 H 9 Cl  = - Δ[C 4 H 9 Cl ]            Δ t Δ = change in  [ ] = mol/L or M Δ[C 4 H 9 Cl] = [C 4 H 9 Cl ] final  - [C 4 H 9 Cl] initial   Δ t = final time – initial time  NEED MINUS SIGN TO MAKE THE RATE POSITIVE Average rate  – reaction rate over an interval of time Instantaneous rate  – reaction rate at a particular time   BOARD DISCUSSION Average rate for the appearance of C 4 H 9 OH  = Δ[C 4 H 9 OH]                Δ t Δ = change in  [ ] = mol/L or M Δ[C 4 H 9 OH] = [C 4 H 9 OH] final  - [C 4 H 9 OH] initial   Δ t = final time – initial time  1
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NOTE: NO MINUS SIGN  Reaction rates and stoichiometry:  aA    +     bB    ---->  cC    +   dD Rate = -1Δ[A]  = -1Δ[B]    =  1Δ[C]  =1Δ[D]   aΔt          bΔt         cΔt         dΔt Example problem 1 RATE LAWS   (CONCENTRATION- RATE EQUATIONS)  are equations that relate the rate of a  reaction to the concentrations or reactants raised to various powers - shows how the rate of   reaction depends on concentration.  (Often called the  differential rate law ) Board discussion. Rate = 
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This note was uploaded on 03/04/2012 for the course PUBH 2113 taught by Professor Edberg during the Fall '11 term at GWU.

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CHAPT14b F10 - Chapter 14 CHEMICAL KINETICS CHEMICAL...

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