CnH2n +Br2= CnH2nBr2
Deduc masa de brom consumata:
initial : 4/100= md/200---> md=8gBr2
final : 2,04/100= (8 -x)/ (200-x)..-----.>X =4g Br2 consumat
niu= 4g/160g/mol= 0,025mol
0,025mol Br2= >0,025 mol alchena
Deduc n: 1,4g= 0,025molx14 n g/mol ---> n=4--> 2 metil-propena