Concentration of two solutions?

Question

The density of toluene (C7H8) is .867g/mL and the density of thiophene (C4H4S) is 1.065g/mL. A solution is made by dissolving 10.0g of thiophene in 250.0 mL of toluene.

(a) calc the mole fraction of thiophene in soln

(b) calc the molality of thiophene in the soln

(c) Assuming that the volumes of the solute and solvent are additive, what is the molarity of the thiophene in the soln.

Thank you .

Answer 1

Moles thiophene = 10.0 g /84.14 g/mol = 0.119

Volume thiophene = 10.0 g / 1.065 g/mL = 9.38 mL

Mass toluene = 250.0 mL x 0.867 g/mL =216.75 g

Moles toluene = 216.75 g / 92.14 g/mol = 2.35

total moles = 0.119 + 2.35 = 2.47

mole fraction thiophene = 0.119 / 2.47 = 0.0482

m = 0.119 / 0.21675 Kg = 0.549

total volume = 9.38 + 250 =259.38 mL > 0.25938 L

M = 0.119 / 0.25938 = 0.459