What is a pseudo first order reaction? Give one example of it.

Explanation:

The reactions which are not first order but become first order under certain conditions are called pseudo first order reactions.

Example: Hydrolysis of esters

Rate = k’[CH₃COOC₂H₅] [H₂O]

Since water is in excess and [H₂O] is constant, so

Here molecularity is 2 and order is 1

Rate = k[CH₃COOC₂H₅] where k = k’[H₂O]

Final Answer: The reactions which are not first order but become first order under certain conditions are called pseudo first order reactions. Where molecularity is 2 and order is 1

Eg. Hydrolysis of esters