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Chemical Kinetics

Question
CBSEENCH12006275

What are Pseudo chemical reaction? Give examples.

Solution
These are the reactions which follow kinetics of lower order whereas by appearance these appear to be reactions of higher order. In other words, these are false or pseudo in nature. In these reactions one of the reactants (genrally water) is reprsent in such a large excess that its concentration remain practially unchanged during the reaction. Therefore, the concentration of such a reactant does not appear in the rate law for the reaction.
Examples: (i)

C12H22O11+H2OH+ C6H12O6 + C6H12O6                                        Glucose      Fructose      reaction rate (r)  = k[Sucrose] [H2O] [H3O]+                                   = k1(Sucrose)

(ii) 
              

CH3COOC2H5+H2OH+ Ethylacetate                                      CH3COOH+C2H5OH                                           Acetic            Ethyl                                            acid               alcohol

reaction rate (r) = kCH3COOC2H5                                                         [H2O] {H3O+]                            = k1(CH3COOC2H5)