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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