14 FoC Catalysts

14 FoC Catalysts - FofC p. 212, Problem 1 Fireflies flash...

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1 FofC p. 212, Problem 1 Fireflies flash at a rate that is temperature dependent. At 29 o C the average firefly flashes at a rate of 3.3 flashes every 10 seconds. At 23 o C the average rate is 2.7 flashes every 10 seconds. Use the Arrhenius equation to determine the activation energy for the reaction that causes the flashing. 0 o C = 273 K R = 8.314 J mol -1 K -1 Hint: Look at the ratio k 29 degrees /k 23 degrees ! a E RT k = A e A)2.5 kJ/mol B)12 kJ/mol C)25 kJ/mol D)150 kJ/mol E)250 kJ/mol 2 1 21 12 2 o- 1 11 1 22 Ea - 1 1 RT ) - RT T RT 1 - 2 a T = 29 C = 302 K, k 3.3/10 = 0.33 s T = 23 C = 296 K, k = 2.7/10 = 0.27 s ke = = e k e take the ln of both sides and solve for E (not log) k ln    a 1 1 -1 1 a 2 a E kR T T k R E = substituting values and using R = 8.3 J mol K k TT E = 25 kJ/mol Summarize info Recognize use of Arrhenius eq.
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3 Model 3: Catalysts, FoC p. 213 KQ 10. What effect does a catalyst have on the activation energy of a reaction? A) increases the activation energy B) decreases the activation energy C) has no effect on the activation energy Energy diagram for a reaction with and without a catalyst. 4 KQ 11. What effect does a catalyst have on the change in free energy of a reaction, G, which is the difference in free energy between the products and reactants? A) increases G B) decreases G C) has no effect on G
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5 KQ 12. What effect does a catalyst have on the mechanism of a reaction? A) changes the mechanism to one that has a lower activation energy B) has no effect on the mechanism, a catalyst just lowers the activation energy
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This note was uploaded on 02/13/2011 for the course CHE 132 taught by Professor Hanson during the Spring '08 term at SUNY Stony Brook.

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14 FoC Catalysts - FofC p. 212, Problem 1 Fireflies flash...

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