What is pseudo first order reaction? Give an example.

Explanation

A reaction whose molecularity is 2 or more but the order is equal to one is called pseudo first order reaction.
`underset("Methylacetate")(CH_(3) COOCH_(3)) + H_(2) 0 underset(H^+) overset("dil HCL or") (to) underset("aceticacid")(CH_3 COOH) + underset("Methylalchol")(CH_2 OH)`
Molecularity `= (1+1) =2` but order `=1` since Rate `alpha [CH_(2) COOCH_(3) ]`
In this reaction water is taken as large excess and hence rate is independent on the concentration of water. So rate depends only on the molar concentration of methyl acetate. Hence it is a first order reaction.