Subst organica - A:CxHyOz
CxHy + (3x-y)/2 O2 ---> x CO2 + y/2 H2O
la 3,12 g A.....6,6 g CO2.....3,24 g H2O
la 104 g A......x * 44 g CO2......y/2 * 18 g H2O
x * 44 = 220=>x=5
y * 9 = 108=>y=12
x=5 si y = 12=>C5H12 = 72g/mol
104-72=32g/mol 32:16=2=>z=2 A:C5H12O2