Unformatted text preview: t always has the same value. Second, T represents the
plus one in the center of the cubic unit ce  eText Main Menu  Textbook Table of Contents pg030 [V] G2 727060 / IRWIN / Schaffer 30 Part I pgm 11498 plm 32198 MP Fundamentals dimensional point of view the reaction rate and the preexponential constant C must have
the same units (since the ratio inside the exponential term must be dimensionless). Finally,
the units for Q and R must be consistent. .......................................................................................................................................
EXAMPLE 2.3–1
Typical activation energies for the reactions described in this text range from 30 to 300 kJ/mol.
Using the value of 30 kJ/mol, calculate the change in the reaction rate when the temperature
increases from 25 C to 100 C. Repeat this calculation using an activation energy of 300 kJ/mol.
Solution / Schaffer Since the problem deals with reaction rates, we must use the Arrhenius equation, 2.3–1. If k T rps
rps 012098
represents the reaction rate at temperature T , then the ratio of the reaction rates at any two
temperatures can be found from the following equation:
k T1
k T2 For Q Q RT1
Q RT2 exp Glossary C exp
C exp Q
R 1
T1 1
T2 30 kJ/mol we ﬁnd: k 100 C
30,000 J/mol
1
1
electrochemical corrosion A liquidsolid degradation
exp
k 25 C
8.314 J/ molK
373 K 298 K
mechanism in which the transfer of electrical charge
exp 2.435
11.4
plays an important role.
Repeating the calculation for Q 300 kJ/mol gives:
electrochemical plating An electrochemical process of
k 100 C
depositing aexp 24.35 3coating. The workpiece is the
thin metal .76 10 10
k 25 C
cathode and the coating material is the anode.
n of a dislocation on its slip
This calculation demonstrates the extreme sensitivity of the reaction rate to changes in either
gers vector and the unit tangent temperature or activation energy. The energy released when an isolated
electron afﬁnity
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This note was uploaded on 02/25/2013 for the course PHYS 2202 taught by Professor Sowell during the Spring '10 term at Georgia Tech.
 Spring '10
 sowell
 Physics, Atom, The Crucible, ........., IRWIN / Schaffer

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