CHEM 135 1st Edition Lecture 9 Outline of Current Lecture I Average rate examples II Rate Law III Reaction Order Current Lecture Examples 1 In the following chemical reaction within first 10 sec N2O5 dropped from 1M to 0 868M Find i Average rate ii O2 t iii N O2 t 2 N2O5 4NO2 O2 Rate 1 N 2 O5 1 NO 2 2 t 4 t i Average Rate ii Rate iii O2 t 1 0 868 1 1 1 N 2O 5 0 0132 0 0066 M s 2 10 0 2 2 t O2 0 0066 M s t 1 N O2 1 N O2 Rate 0 0066 0 0264 m 1 4 t 4 t 2 H2O2 can be used as a disinfectant it decomposes as 2 H2O2 2H2O O2 if the rate of appearance of O2 is 0 0014 Ms 1 what is the rate of disappearance of H2O2 Answer 0 0028 Ms 1 These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 3 In the first 10 0 seconds of the reaction the concentration of I dropped from 1 000M to 0 868M a Calculate the average rate of this reaction in this time interval b Determine the rate of change in the concentration H2O2 aq 3 I aq 2H aq I3 aq 2H2O l I 1 H2 O 3 t 2 t H H 2 O2 t a Rate 1 t I t 2 1 3 I 1 0 868 1 4 4 10 3 M s Rate 3 10 1 3 b Rate H 1 2 H 4 4 10 3 1 2 2 3 8 8 10 M s Rate Law and Reaction Order Rate Law Rate K reactant n K constant Reactant concentration of reactant n reaction order rate law is only with reactants NO PRODUCTS Reaction order tells the relation between the rate and the concentration of the reactant n is not the coefficient n is found experimentally n cannot be predicted A When n 1 first order reaction A yB The rate changes by the same factor as the concentration x Rate K A K 1 s Ex A Rate M s 0 1 30 0 2 60 0 6 180 B When n 2 second order reaction xA yB The rate changes by the square of the factor Rate K A 2 K M 1S 1 C When n 0 zero order reaction Rate remains constant Rate K K M s
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