Lecture 6

Md Kausher ahmed Instructor Electrical department

Chemistry 5913

Previous lesson Chemical reaction Explanation

Lesson declared Catalyst

Learning outcomes After finished this lesson student will able to (1)Say what is catalyst. (2)Say type of catalyst. (3)Say effect of catalyst. (4)Explain how do the catalyst work.

Catalyst A catalyst is a substance that speeds up the rate of a chemical reaction but is not consumed during the course of the reaction. A catalyst will appear in the steps of a reaction mechanism, but it will not appear in the overall chemical reaction.

Types of Catalysts Catalysts in the same phase are called homogeneous catalysts, while those in different phases are called heterogeneous catalysts.

Effect of catalysts The effect of a catalyst is that it lowers the activation energy for a reaction. Generally, this happens because the catalyst changes the way the reaction happens (the mechanism). We can visualize this for a simple reaction coordinate in the following way.

Catalyst reaction curve

Catalyst reaction progress curve

How do catalysts work image

How do catalysts work The possibilities for how a catalysts actually works are endless. Some catalysts actually change during the course of the chemical reaction, but then are returned to their original state at the end of the reaction. For example, MnO 2 catalyzes the decomposition of H 2 O 2 to water and oxygen gas by the following mechanism.

Feedback #What is catalyst.? #How do it’s work.? #Explain types of catalyst.

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