100g compus CxHyBr.....40,81/12molC....4,76/1molH.....54,42/80molBr
12x+y+80 g.........................x........................y.......................1.
rezulta trei ecuatii in x si y; prin rezolvarea lor. x= 5, y=7
a)C5H7Br
b)Poate proveni din pentina sau pentadiena--> NE=2
c) A SI B
C≡C-C-C-C SAU C=C=C-C-C