Catalyst: A substance that can influence the rate of a chemical reaction but itself does not undergo the permanent chemical change.
Catalyst increases the reaction rate by lowering the activation energy of the reactant.
Eq → Activation energy without catalyst
Eq → Activation energy with catalyst
ER → Energy of reaction
A → Path of reaction without catalyst
B → Path of reaction with catalyst.
Catalysis: The process in which rate of reaction is influenced by catalyst is called catalysis.
Substrate: The reactant on which catalyst acts is called substrate.
Catalyst does not change the heat of reaction it only makes a process faster.
Catalyst does not change the yield of the product
Type of Catalyst:
Positive Catalyst: A catalyst which increase the rate of reaction by lowering the activation energy of reaction.
Example :
Negative Catalyst: A catalyst that retards the chemical reaction by raising the energy barrier or activation energy.
Example:
Types of catalysis
Homogeneous Catalysis: Catalysis in which catalyst and reactants are present in same phase.
Example:
Heterogeneous Catalysis: Catalysis in which Catalyst and reactants are in different phase.
Example:
Effect of catalyst on the Rate of Reaction:
According to the Arrhenius theory
Thus specific rate of reaction (rate constant k) depends upon two factors
- Ea
- T
when we employ catalyst Ea of reaction is lowered and more no. of molecules possesses energy above the threshold temperature rate of reaction increases.
If at temperature T rate constant is K1 for uncatalyzed reaction and rate case is K2 for catalyzed reaction
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Class 12 Chemistry Chemical Kinetics All Topics Notes CBSE Class 12 Chemistry All Chapters Notes
