What is the name given to the first order reactions whose molecularity is not one but behaves like one?  

Pseudo-unimolecular reactions

Those first order reactions whose molecularity is not one but behaves like one are called Pseudo-unimolecular reactions.

Example:

(i) Hydrolysis of an ester :

    CH₃COOC₂H₅ + H₂O → CH₃COOH + C₂H₅OH

    - \(\frac{dx}{dt}\) = k[CH₃COOC₂H₅]

So, order of reaction is one.