Untitled - Kelly Walsh High School

196 CHEMISTRY FOR THE UTTERLY CONFUSED
Quick Tip
ln (1.122159 10 5 )
B(1.80180 103 1.2804097 103 )a 1
b R
K
11.62818
E a
8.314 J/mol K
E a
8.314 J/mol (5.21392 104 )
(11.62818) (8.314 J/mol)
Ea
(5.21392 104 1.85420 10
)
5 1.9 105 J/mol
Activation energy values are normally large, positive values. If your answer
doesn’t meet these two conditions, you probably made an error in your calculation.
If your answer is negative, the most likely error is that you incorrectly
paired k 1 and T 1.
High activation energies are normally associated with slow reactions. Anything
done to lower the activation energy of a reaction will tend to speed up the reaction.
13-5 Catalysis
A catalyst is a substance that speeds up the rate of reaction without being consumed
in the reaction. A catalyst may take part in the reaction and even change
during the reaction, but at the end of the reaction, it is at least theoretically
recoverable in its original form. It will not produce more of the product, but it
allows the reaction to proceed more quickly. In equilibrium reactions, the catalyst
speeds up both the forward and reverse reactions. Catalysts speed up the
rates of reaction by lowering the activation energy of the reaction. In general,
there are two distinct types of catalysts.
Homogeneous catalysts are catalysts that are in the same phase or state of matter
as the reactants. They provide an alternate reaction pathway with a lower
activation energy.