# Universal constant that is it always has the same

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Unformatted text preview: t always has the same value. Second, T represents the plus one in the center of the cubic unit ce | e-Text Main Menu | Textbook Table of Contents pg030 [V] G2 7-27060 / IRWIN / Schaffer 30 Part I pgm 1-14-98 plm 3-21-98 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 01-20-98 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 liquid-solid degradation exp k 25 C 8.314 J/ mol-K 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.

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