2.2 Calculate the mole fraction of benzene in solution containing 30% by mass in carbon tetrachloride.

Let the total mass of the solution be 100 g and the mass of benzene be 30 g.

Mass of carbon tetrachloride = (100 − 30)g = 70 g

Molar mass of benzene (C6H6) = (6 × 12 + 6 × 1) g mol−1 = 78 g mol−1

NumberofmolesofC6H6=3078mol=0.3846mol

Molar mass of carbon tetrachloride (CCl4) = 1 × 12 + 4 × 355 = 154 g mol−1

NumberofmolesofCCl4=70154mol=0.4545mol

Thus, the mole fraction of C6H6 is given as:

NumberofmolesofC6H6NumberofmolesofC6H6+NumberofmolesofCCl4
=0.38460.3846+0.4545
=0.458