CHEM 104 1st Edition Lecture 14 Rate Law Rate Law relationship between rate of reaction and concentration of reactants Rate laws are determined experimentally General procedure to find rate law o aA bB X Rate k A m B n k rate constant m reaction order with respect to A n reaction order with respect to B m n overall reaction order k depends on temperature and has a fixed value at a given temperature There are two main methods for determining rate laws Initial Rates Method and Integrated Rate Law Method Example of Initial Rates Method o 5 experiments performed of the reaction 2NO g O2 g 2NO2 g o Experiments 1 and 2 NO was constant O2 doubled and the initial rate doubled reaction order of O2 is 1 o Experiments 2 and 4 O2 was constant NO doubled and the initial rate quadrupled reaction order of NO is 2 o Rate k NO 2 O2 o Overall order is 2 1 3 o Calculate k in all of the experiments by plugging in known numbers then average to find k o Rate 7 07 103M 2s 1 NO 2 O2 General Integrated Rate Law Method for first order reactions o A products o Rate change in A change in t k A 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 dA dt k A dA A kdt integral from 0 to t ln A t kt ln A 0 Example of General Integrated Rate Law Method o K 0 21 sucrose 0 01 M how long does it take to drop 90 i e to 0 001M o Ln 0 001M 0 21 t ln 0 01M solve for t
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