An aqueous antifreeze solution is 40.0% ethylene glycol (C2H6O2) by mass. The density of the solution is 1.05 g/cm3. Calculate the molality, molarity, and mole fraction of the ethylene glycol.

Question

molality

I actually can do this whole problem EXCEPT for one part I'm stuck on. The part I'm stuck on is when you assume the solution is 1000 g, whether you should or shouldn't multiply by the density (1.05 g/cm3).

For example, assuming 1000 g of solution gives you:

600 g H2O (1 mol H2O/18.02 g H2O) = 33.3 mol H2O

vs.

Assuming 1000 g of solution times the density (1050 g of solution), which would actually make H2O 630 g:

630 g H2O (1 mol H2O/18.02 g H2O) = 35.0 mol H2O

This slight difference would be considered big to my professor.