Question

Functional group present in C2H5Cl

Answer 1

Functional group present in C2H5Cl  is a halogen 

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chloro is the functional group present in  C2H5Cl

the name of compound is chloro ethane

Answer 2

Basically C2H5Cl comes under Halo Group but in the category of Halo group it comes under Chloro group. The IUPAC name of C2H5Cl is chloroethane and it's common name is ethyl chloride.
Hope this helps you !