Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Craftylikeafly on January 30, 2010, 06:33:54 PM
-
A solution of caffeine (C8H10N4O2) in chloroform (CHCl3) as a solvent has a concentration of 7.10*10^-2m.
I know that i have to convert the molality to grams somehow to get the mass of the solute but i am stuck, please help with detail, i also know the m=mols of solute/kg of solvent, caffeine is the solute and the chloroform is the solvent and the mass %= mols of solute/total mass*100
-
Have you tried assuming a given amount of solvent?
EDIT: I would double check your % mass formula.
-
I still dont understand :(
-
Assume 1kg of chloroform is the solvent.
Molality = (mol of solute) / (kg of solution)
So now you should have mol of solute. Use stoichiometry from there to get the mass of caffeine in this solution.
% Mass = (Mass of solute) / (Mass of Solute + Mass of Solution)
Remember we assumed a mass of solution in the first step.
Hopefully this is more helpful. :)