CHEM 104 1st Edition Lecture 14Rate 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]nk = 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 1o 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 = 3o Calculate k in all of the experiments by plugging in known numbers, then average to find ko 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
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