posted by jimbo .
An aqueous solution containing 12.0% MgCl2 by mass has a density of 1.105g/ml. What is the mol fraction of water in this solution?
12% MgCl2 means 12 g MgCl2 in 100 g solution. Use the density to calculate the volume of 1000 mL.
1.105 g/mL x 1000 mL = 1105 grams.
1105 x 0.12 = 132.6 g MgCl2 and
1105-132.6 = ?? g H2O
moles H2O = grams/molar mass H2O
moles MgCl2 = g MgCl2/molar mass MgCl2.
XH2O = moles H2O/total moles.
Post your work if you get stuck.