what is the molality of a 10.5% by mass glucose (C6H12O6) the density of the solution is 1.03 g/ml. i got up to m = 0.058281527 mol/ kg... please help !!!!

Question

anonymous · Answer

Ok, to do this you first have to calculate how many moles there are in a litre: multiply the density by 1000 to convert from millilitres to litres and you have 1.03kg. If the strength of the solution is 10.5% then there will be 105g per 1.03kg. One mole of glucose is (6x12)+(12x1)+(6x16) or 180g. 105/180= 0.5833 (or 7/12). So the molarity would be 0.5833moles per litre.

However, we're not looking for molarity but we are after the molality - so we need the number of moles per kilogram of solute (note this is not the mass of the solution). Water has a density of 998.2g/l at 20 centrgrade so the molality would be 0.5833 over .998.

anonymous · Answer

ok ok thank you so much!