monoclortoluen : C7H7Cl M=7*12+7+35.5=126.5 diclortoluen: C7H6Cl2 M=7*12+6+35.5*2=161 Se considera 100 g amestec monoclortoluen si diclortoluen. (x+y=100)  126.5 g monoclortoluen ...... 35.5 g Cl     x g monoclortoluen ...........  a g Cl  = 35.5x/126.5  161  g diclortoluen    .........  35.5*2 g Cl     y g diclortolue ................    b g Cl  =  35.5*2y/161 a+b = 40 ( amestecul are 40 % Cl - ipoteza) <=> 35.5x/126 + 35.5*2y/161 = 40 <=> 0.28x+0.44y=40 x+y=100 => x=100-y Inlocuim in prima relatie => 0.28(100-y)+0.44y=40 <=> 28-0.28y+0.44y=40 <=> y=75 ; x=100-75 = 25 Amestecul contine 25% monoclortoluen si 75% diclortoluen.