Class Note for CHEM 112 at UMass(40)
Class Note for CHEM 112 at UMass(40)
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This 8 page Class Notes was uploaded by an elite notetaker on Friday February 6, 2015. The Class Notes belongs to a course at University of Massachusetts taught by a professor in Fall. Since its upload, it has received 10 views.
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Date Created: 02/06/15
Determining 21 Reaction Rate Blue dye is oxidized with bleach The rate the change in dye concentration with time can be determined from the plot Dye Com Following reaction progress For the reaction ZNZO5 gt 4N02 02 we can follow the progress by monitoring 0 the rate of formation of N02 0 the rate of formation of O2 andor 0 the rate of disappearance of N205 10 Determining an Instantaneous Reaction Rate 15 min to decyease N205 from 122 m 110 N205 matL 0 10 20 30 40 50 60 70 80 90 10 11 Time t hours 1 1 Determining an Average Reaction Rate 1150 1393 15 min to damage 120 MNEOE from 122 n 110 110 100 090 080 quot205 moiL 0 10 20 30 AU 50 50 70 80 90 10 11 Time t hours 12 Determining an Reaction Rate for 21 Period of Time 140 c 15 min to decrease 7 120 gtr1205 from 122m 11a 11a 0 10 20 30 40 50 60 70 80 90 10 11 Time t hours 13 Factors Affecting Rates 1 Concentrations 2 Physical state of reactants and products 3 Temperature 4 catalysts 14 Concentrations and Rates To determine a reaction s mechanism we study the reaction s rate and concentration dependence 15 Concentrations and Rates Take reaction where CI39 in cisplatin PtNH32CIZ is replaced by H20 PtNH32C2aq H20 4 PENH32H20CUBQ CHM r at if 6 J J H J owl J aquot 15 Concentrations amp Rates Rate of reaction is proportional to PtNH3zCz We express this as a RATE LAW where k rate constant k is independent of conc but increases with T Concentrations Rates amp Rate Laws In general for The exponents m and n o are the reaction order 0 can be 0 1 2 or fractions 0 must be determined by experiment Not necessarily the coefficients for the reaction Interpreting Rate Laws Rate k AmBn Ifm 1 rxn is 1st order in A If A doubles then rate goes up by factor of If m 2 rxn is 2nd order in A Doublin A increases rate by If m 0 rxn is zero order If A doubles rate 19 Deriving Rate Laws Example Derive the rate law and k for CHscHOg gt CH4ltggt 009 from experimental data for rate of disappearance of CH3CHO EXpt CH3CHO Rate of disappearance of mo CH3CHO moiL39sec 1 010 0020 2 020 0081 8 080 0182 4 040 0318 20 Deriving Rate Laws Rate of rxn k CH3CHO2 Here the rate goes up by when initial conc doubles Therefore we say this reaction is order Now determine the value of k Use expt 3 data Using k you can cac rate at other values of CH3CHO at same T 21 Reaction Rate Constants Zero order reaction k are moiLo time First order reaction k are time391 Second order reaction k are Lmol 0 time 22 0091 N02g gt C3029quot N02g The initial rate of the reaction above was measured at 25C for various initial concentrations of CO and N02 Determine the rate equation the rate constant and the units of the rate constant Initial Concentrations Initial Rate Experiment 0 molL N02 mulL molL h 1 51ogtlt 10quot o350gtlt1c A 34x1o 5 2 51ogtlt 10quot 07oox10quot 63X10398 3 510 x 10quot 0175 gtlt 10 A 17 x 10 8 A 102gtlt 10 3 0350x10quot 63X10398 5 153 x 10 3 0350 gtlt 10 A 102 X 10 3 23
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