You have been given a solution containing chloroform and toluene, the concentration of chloroform is specified as 40 mole percent, toluene 60 mole percent. what is the mass percentage of chloroform in this solution?

In 1 mole of mixture

0.4 mole of chloroform (CHCl3), mass = 0.4*119.5=47.8g chloroform

0.6 mole toluene C7H8, mass = 0.6*92=55.2 g toluene

mass of solution 47.8+55.2=103 g

mass% of chloroform = (47.8/103) * 100%=46.4%

mass%of toluene = (55.2/103) * 100%=53.59%