How do you calculate the molar mass of a compound?

Calculate the molar mass of the unknown compound.?

• An aqueous solution containing 36.7g of an unknown molecular (nonelectrolyte) compound in 152.3g of water was found to have a freezing point of -1.3∘C.

• Answer:

  use the equation .. dTfp = Kf x m x I where .. dTfp = change in freezing point = fp pure solvent - fp solution .. .Kf = cryoscopic constant of the solvent = 1.86°C/m for H2O .... m = molality = moles solute / kg solvent ... .i = van't hoff factor = # ions 1 unit of solute dissociates into i = 1 for this case because the statement non-electrolyte implies the solute does not dissociate. ***** so.. .. (1) determine "m" .. (2) convert 152.3g H2O to kg H2O to moles solute (via "m") .. (3) molar mass = mass solute / moles solute