[BrittanyD]

 determining the molecular weight of a substance (e.g MgCl)

To do that I plan on making standard solutions of sodium chloride at different concentrations. Then measure the freezing points so I can make a straight line graph. Then I'd make a solution of whatever substance i wanted to find the molecular weight of (e.g MgCl) and measure its freezing point. From there I would work out its molecular weight by using the line graph I had prepared earlier with appropriate calculations and formulas.

Does anyone know these calculations/formulas??
anyone have a method to do this?? im a bit lost..

(I'm only 15 and am finding this all a bit complex..)

[Borek]

To some extent you are on the right track, but you can still miss big. Do you know what equation describes the freezing point depression? Do you know what Van't Hoff factor is? Do you know right formula for magnesium chloride (hint: it is NOT MgCl)?