Question

Calculate the mole fraction of ethylene glycol. In the solution containing 20% by mass.

Answer 1

ethylene glycol -> C₂H₆O₂

20% of C₂H₆O₂ by mass is present.
That means solution has 20 g of ethylene glycol and 80 g of water.
Now,
Molar mass of C₂H₆O₂ = 12 x 2 + 1 x 6 + 2 x 16 = 62 g mol^-1 .
Moles of C₂H₆O₂ n1 = 20 / 62 = 0.322 moles
Moles of water n2 = 80 / 18 = 4.444 moles
Mole fraction of ethylene glycol =Moles of ethylene glycol / total no. of moles
= n1 / n1+n2
= 0.322 / (0.322 + 4.444) = 0.068