The reaction involes is as follow:
−NH2+Cl−O||C−CH3→−NH−O||C−CH3
For one −NH2 group, increase in molecular mass
=(43−1) g/mol=42 g/mol
Molcular mass of CH3CO=43 g/molAtomic mass of H=1 g/mol
Actual increase in molecular mass of compound
=(348−180) g/mol=168 g/mol
∴No. of NH2=168/42=4