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

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

Solution

Mass % is given so take total mass of the solution = 100 g

Then the mass of benzene      = 30 % of 100 = 30 g.

Mass of carbon tetrachloride   =  total mass  - mass of benzene

=(100 − 30)g

= 70 g

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

Use the formula 

Number of moles of C₆H₆ = 30 /78 = 0.3846 mol

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

Use same formula again we get 

Number of moles of CCl4 = 70/154 = 0.4545 mol

Use the formula of mole fraction 

Mole fraction of benzene =0.3846 /(0.3846+ 0.4545) = 0.458