17_kinetics_rates (2)

The lower the activation energy the faster the

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Unformatted text preview: ion hot cold • Generally, as temperature increases, so does the reaction rate. • This is because k is temperature dependent. 24 11/20/2013 Effect of Temperature k (T ) Ae E a RT activation energy temperature cold warm gas constant pre-exponential factor linearize by taking natural log of both sides lnk (T ) Ea R 1 ln A T Mg metal in water a plot of ln(k) vs 1/T has a slope of -Ea/R ***use T in Kelvins Most Common Rate vs Temperature 25 11/20/2013 The following table shows the rate constants for the rearrangement of methyl isonitrile at various temperatures (these are the data in Figure 14.12): (a) From these data, calculate the activation energy for the reaction. (b) What is the value of the rate constant at 430.0 K? (a) convert temperature to K, calculate 1/T and ln(k) A graph of ln k versus 1/T results in a straight line.. lnk (T ) Ea 1 ln A R T (b) To determine the rate constant, k1, at T1 = 430.0 K, we can use Equation 14.21 with Ea = 160 kJ/mol, and one of the rate constants and temperatures from the given data, such as k2 = 2.52x10–5 s–1and T2 = 462.9 K: ln k1 Note that the units of k1 must be the same as those of k2. Ea ln A RT1 Ea ln k 2 ln A RT2 ln k1 ln k 2 ln Ea Ea ln A RT ln A RT1 2 k1 Ea k2 R 1 1 T T 1 2 26 11/20/2013 → Transition State Theory ⇄ ‡ → activated complex ‡ ‡ / ‡ / c0= is standard state concentration (1 M) / ‡ ‡ ‡ Whole thing can also be written with a partition function including temperature ‡ ‡ ‡ Δ‡ Δ‡ Δ‡ Δ 2 ‡ / / 27 11/20/2013 Other Rate vs Temperature Profiles chain reaction enzyme controlled reaction, Michaelis/Menten 28...
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