Why hydrolysis of Sucrose is called pseudo uni-molecular reaction ?

Dear Student,

Hydrolysis of sucrose is a pseudo-unimolecular reaction because here the water present is in excess and so its rate is dependent only on the concentration of sucrose. Hence, the reaction becomes unimolecular instead of bimolecular. 

$$\begin{gathered} \mathrm{Sucrose}+{\mathrm{H}}_2\mathrm{O} \to \mathrm{Glucose}+\mathrm{Fructose} \\ \mathrm{Rate}=\mathrm{k}\left[\mathrm{Sucrose}\right] \end{gathered}$$