**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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