Chemistry
posted by Anonymous .
Find the Molality and Molarity of a solution where 1.0g of NaCl was dissolved in 100mL of rubbing alcohol (the density of the alcohol is 0.78 g/mL).
Not sure what steps to use to find Molarity and Molality....

100 mL alcohol has what mass?
mass = volume x density = 100 x0.78 = 780g or 0.780 kg.
mols 1.0 NaCl = 1.0/molar mass NaCl.
m = mols/kg solvent = ?
In order to calculate M you should know the density of the solution and you don't have that. I know the density of the alcohol is given but that isn't the density of the solution. To work the problem we must assume the volume of the soln is the same as the volume alcohol added. It won't be but it will be close.
Then M = mols NaCl/0.1L = ?