Pseudo First Order Reaction: The reactions which are not truly of first order but become reactions of first order under certain conditions are called pseudo first order reactions. For example,
·       Hydrolysis of ester in acid (H+).
CH3COOC2H5 + H2O → CH3COOH + C2H5OH
Rate = k [CH3COOC2H5] [H2O]
Since water is in excess so its concentrations remains same during reaction and [H2O] is constant and rate is independent of c0ncentration of H2O so

Rate = k[CH3COOC2H5], Where k = k’[H2O]


·       Inversion of cane sugar (in acid)
C12H22O11 + H2O    C6H12O6   +    C6H12O6                 
Cane sugar                 Glucose        Fructose
Since water is in excess and [H2O] is constant, so
Rate = k [C12H22O11]


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