Answer: The molecular weight of this compound is 288.4 g/mol
Step-by-step explanation:
As the relative lowering of vapor pressure is directly proportional to the amount of dissolved solute.
The formula for relative lowering of vapor pressure will be,

where,
= relative lowering in vapor pressure
i = Van'T Hoff factor = 1 (for non electrolytes)
= mole fraction of solute =

Given : 7.745 g of compound is present in 159.9 g of diethyl ether
moles of solute =

moles of solvent (diethyl ether) =

Total moles = moles of solute + moles of solvent =

= mole fraction of solute =



Thus the molecular weight of this compound is 288.4 g/mol