d(aer) = miu(hidrocarbura)/miu(aer)
=> miu(hidroc.) = d(aer)xmiu(aer) = 2,69x28,9 = 78 g/mol
100 g ....... 92,31 g C ....... 7,69 g H
78 g .......... a g C ................ b g H
=> a = 72 g C
=> b = 6 g H
=> nC = 72/12 = 6
=> nH = 6/1 = 6
=> Fm = C6H6 = benzen