A solute, which has i = 5, is placed in 5430 g of nitrobenzene. If the freezing point is lowered to 3.29°C...

Question

A solute, which has i = 5, is placed in 5430 g of nitrobenzene. If the freezing point is lowered to 3.29°C and the mass of the solute is 37.8 g, find the molecular weight.

Answer 1

5430g as a litter of nitrobenzene has a mass of 1199g , corresponds to a volume of 4.528l , the concentration is so
37.8/4.528 =8.35g/L
the cryoscopic constant of nitrobenzene is -8.1°/osmole
the osmolarity of the solution is 3.29/8.1 =0.406 osmole
The number of osmole is Osm = mole*i
so the molarity is 0.0812
molarity =c/M
M=c/molarity

M= 8.35/0.0812=103g