Răspuns:
FeCl₃
C₆H₆ + xCl₂ ---> C₆H₆₋ₓClₓ + xHCl
rap. masic C:H=18:1 corespunde compusului clorurat.
raportam la H: 1/18+1= 6-x/6*12+6-x ( μ compus clorurat fara continut de clor intrucat raportul care corespunde e doar C;H)
<=> 1/19=6-x/78-x
=> 78-x=19(6-x)
<=> 78-x=114- 19x
<=> 18x= 36 => x=2 => F.ch.M: C₆H₄Cl₂