With the help of an example explain what is meant by pseudo first order reaction.
A reaction in which one reactant is present in large amount and its concentration does not get altered during the course of the reaction, behaves as first order reaction. Such reaction is called pseudo first order reaction.
e.g., (i) hydrolysis of ethyl acetate
conc. CH3COOC2H5+H2OH+⟶CH3COOH+C2H5OHConc.t=0Conc.at t 0.01 mol0 mol 10 mol9.99mol 0 mol0.01 mol 0 mol0.01 mol
Rate of reaction = k [CH3COOC2H5]
where, k=k′[H2O]
e.g., (ii) inversion of cane sugar
C12H22O11+H2OH+⟶C6H12O6+C6H12O6Rate of reaction=k[C12H22O11]where k=k′[H2O]