i was told by another source that i could do the following, which seems less complicated than what you are telling me to do, but i appreciate the help.
Step 1: Use DTf = Kf x molality to solve for the molality (both Kf and the change in freezing point (DTf) are known.
Step2: Use the molality formula (molality = moles of solute/kg of solvent) to solve for moles of solute. The molality is known from Step 1 and kg of solvent = .200 kg from the problem.
Step 3: Use the fact that molecular weight = mass of solute/moles of solute to find the mol weight of the solute. The mass of solute is given as 6.0g and the moles were calculated in step 2.
Step 4: Determine the number of empirical formula units in a molecule by dividing the mol weight (determined in step 3) by the emp. formula mass (CH2 = 14g/mol). The results of this division will give you x in (CH2)x.
i understand everything except step one. i dont have DTf...i only have Kf= 5.12 degrees C/m for benzene and that the freezing point of the solution is 1.83 degrees C below that of pure benzene. The freezing point of pure benzene is 5.5°C, which i looked up. So to get DTf, do i subtract 5.5 - 1.83= 3.67°C...right?? or am i missing something...?