Class 12 Chemistry Chemical Kinetics Pseudo order reaction

Pseudo order reaction

The reaction that appears to be an nth order reaction but belongs to some different order is called Pseudo order reaction.

For example, a pseudo first order reaction is a chemical reaction between two reactants participating in a chemical reaction and therefore should be a second order reaction. But it resembles to be a first order reaction due to the presence of reactants in negligible quantity.

Let R` + R`` --> P

Rate = k[A]1[B]1

Order of reaction = 2.

Let us consider another reaction,

CH3Br + OH→ CH3OH+Br

Rate law for this reaction is

Rate = k [OH][CH3Br]

Rate = k [OH][CH3Br] = k(constant)[CH3Br]=k′[CH3Br]

As only the concentration of CH3Br would change during the reaction, the rate would solely depend upon the changes in the CH3Br reaction.

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