CSU CHEM 113 - Catalysis (2 pages)

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Catalysis, speeding up reactions.

Lecture number:
Lecture Note
Colorado State University- Fort Collins
Chem 113 - General Chemistry II

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CHEM 113 9 15 Lecture 9 Outline of Last Lecture I More practice of reaction mechanisms Outline of Current Lecture II Catalysts a Homogenous b Heterogeneous c Enzymes Current Lecture 16 7 Catalysis Speeding up a Reaction Catalyst increases the reaction rate without itself being consumes in the reaction o It generally provides a different reaction pathway with lower total activation energy than the uncatalyzed reaction o It speeds up the forward reaction as well as the reverse reaction o However it does not affect the change in H because the actual difference in energy is still the same It s like saying 6 4 2 and 4 2 2 The difference is still the same you are just working with different values Homogeneous catalysis o A homogeneous catalysis exists in solution with the reaction therefore it must be in the same phase as the reactant Heterogeneous catalysis o A heterogeneous catalysis speeds up a reaction in a different phase from the reactants These are usually a solid catalyst and gas or solution reactant The reaction happens on the surface of the catalyst Metals catalyze by chemically absorbing the reactants onto their surface Enzymes o Enzymes are protein catalyst o They behave like both types of catalysts These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute An enzyme provides a surface on which one reactant is temporarily immobilized to wait until the other reactant lands nearby like heterogeneous catalysts The active site groups where the substrate binds interact with the substrate s in multistep sequences in the presence of solvent and other species like many homogenous catalysts o They are incredibly efficient in terms of the number of reactions catalyzed per unit time o They are also very specific to the reaction they are catalyzing o Models of enzyme reaction Lock and Key model This model visualizes the enzyme active site having a fixed shape The shape matches

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