Question

The mole fraction of benzene in a solution in toluene is 0.40. Calculate the weight percent of benzene in the solution.

Answer 1

Given: Mole fraction of benzene `chi_"benzene"` = 0.40

Therefore, mole fraction of toluene = 1 − 0.40 = 0.60

Molar mass of benzene (C₆H₆) = 78 g/mol

Molar mass of toluene (C₇H₈) = 92 g/mol

Let the total moles of solution be 1 mol.

Then,

Moles of benzene = 0.40

Moles of toluene = 0.60

Then,

Mass of benzene = 0.40 × 78 = 31.2 g

Mass of toluene = 0.60 × 92 = 55.2 g

Total mass = 31.2 + 55.2 = 86..4 g

Weight % of benzene = `(31.2/86.4) xx 100`

= 36.11%

∴ The Weight % of benzene in the solution is 36.11%.