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molality, mole fraction, and molarity

Submitted by sueyoung20 on Wed, 02/29/2012 - 02:49

I don't know how to this problem!

please show all the work..!

 

Question: a solution containing equal masses of glycerol(C3H8O3) and water has a density of 1.10 g/mL. Calculate

a) the molality of glycerol

b)the mole fraction of glycerol

c) the molarity of glycerol in the solution


So you have 1kg of glycerol per kg of water. Find molar mass of glycerol and find the number of moles glycerol in 1000 g (1kg). This is molality (moles of solute per kg of solvent)

Mole fraction - find the molar mass of water. Find moles of water in 1000g. Add moles of water to moles glycerol to get total moles. Mole fraction of glycerol = moles glycerol/total moles

Mass of solution (assuming 1kg of each) = 2kg or 2000g. From density, this will have a volume of 2000/density. Now you know volume, and you know the number of moles of glycerol in 1kg of glycerol, molarity = number of moles/volume of solution in L