Q.Explain pseudo-first order reaction with suitable example.

A pseudo-first order reaction is one whose stoichiometry suggests a higher order, but which is observed experimentally to follow first order kinetics. The classic example is the acid hydrolysis of methyl acetate, $CH_3COOCH_3+H_2O\rightarrow CH_3COOH+CH_3OH$: its true rate law is $\text{rate}=k'[CH_3COOCH_3][H_2O]$, genuinely second order overall. But water, present here both as reactant and as the solvent, is in such enormous excess that its concentration barely changes during the reaction and can be treated as an effective constant, $k''=[H_2O]$. The rate law then collapses to $\text{rate}=k'[CH_3COOCH_3]k' …