Posted by paula on Saturday, February 12, 2011 at 8:58pm.
what is the molality of a solution of 50.0 grams of propanol in 152 mL water if the density of wate is 1.0 g/mL and the density of the solution is 0.78 g/mL

chem  DrBob222, Saturday, February 12, 2011 at 9:33pm
m = moles/kg solvent
moles propanol = g/molar mass propanol = ??.
m = ??moles/0.152 
chem  paula, Sunday, February 13, 2011 at 12:03am
I am not sure what to do with the density of the solution of 0.78 g/mL.
The answer I came up with is 5.47 mol/kg. I found the density of the water in grams then I converted it to kg (152 x .001 = .152. I divided 50 g by the molar mass of 60.09502 g/mol = .8320 moles. Next, I divided that by .152. However, I didn't use the .78 g/mL beacause I am not sure what to do with it. Please explain. 
chem  DrBob222, Sunday, February 13, 2011 at 1:43am
5.47 molal is correct. You don't need the density of the solution.