Ch_13_IV_Catalysis

Ch_13_IV_Catalysis - Second Example Heterogeneous Catalyst...

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A catalyst is a substance that increases the reaction rate, but is not consumed in the reaction. A catalyst provides a new and easier pathway for the reaction. Note, both the rate of the forward and reverse reaction are increased— No change in amount of final product .
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E15 Example of Homogeneous Catalyst (same phase) Plausible mechanism Called?
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Second Example of Homogeneous Catalyst 2Ce 4+ (aq) +Tl + (aq) 2Ce 3+ (aq) +Tl 3+ (aq) (very slow) rate = k [ Tl + ][ Ce 4+ ] 2 •Simultaneous transfer of 2 e - •2 Ce 4+ ions simultaneously near Tl + (3-body encounter) •10 -5 times as likely as 2-body encounters) Manganese ion: Mn 2+ (aq) (most stable) Mn 3+ (aq) Mn 4+ (aq) (slow) Ce 4+ (aq) +Mn 3+ (aq) Ce 3+ (aq) +Mn 4+ (aq) (fast) (fast) Tl + (aq) +Mn 4+ (aq) Tl 3+ (aq) +Mn 2+ (aq) rate =k cat [Ce 4+ ][Mn 2+ ] Allows 2-body Encounters Ce 4+ (aq) +Mn 2+ (aq) Ce 3+ (aq) +Mn 3+ (aq) E19 FE21
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Heterogeneous Catalyst (different phases) 2H 2 (g) + O 2 (g) 2H 2 O(g) •Large E a •Spark •Flame H 2 gas Pt gauze Common metallic catalyst: Pt, Pd, and Ni
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Unformatted text preview: Second Example Heterogeneous Catalyst The arrangement of a catalytic converter in an automobile. A cutaway view of a catalytic converter, showing the pellets of finely divided transition metal catalyst. (Up to 1 mole of CO 2 per minute) (large surface area) Whitten p. 648 Simplification of the catalysis of the reaction CO (g) and O 2 (g) to make CO 2 (g). Whitten p. 649 Third Example Heterogeneous Catalyst (oversimplification) The cigarette ash contains trace amounts of metal compounds that catalyze the combustion of sugar. A sugar cube rubbed in cigarette ash A sugar cube Burns Melts at 185C Fourth Example Heterogeneous Catalyst Whitten p. 650 Simplified Lock-and-key Mechanism for Enzyme Reaction Enzymes: Proteins that act as Catalysis Whitten p. 650 Example of lock-and-key theory Example of an Enzyme...
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This note was uploaded on 03/08/2011 for the course CHEM 126 taught by Professor Biolsi during the Spring '08 term at NJIT.

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Ch_13_IV_Catalysis - Second Example Heterogeneous Catalyst...

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