alchena are formula generala CnH2n si m%C:
14n,g alchena.......12n,gC
100g....................m%,c= 1200/14
m%C,alcool/ 1200/14=0,7---> m%C,alcool= 60
presupun ca este un alcool saturat cu formula generala CnH2nO
14n+18, g alcool...........12n,gC
100g.................................60
1200n= 840n+ 1080----> n=3=====> propanol si propena