15.0 g of an unknown molecular material was dissolved in 450 g of water. The resulting solution was found to freeze at -4.34oC. What is the molar mass of this material?

(b) Given mass of solute=wb=15.0g
Molar mass of solute=Mb=?
Mass of water=wa=450g
Freezing point of water=0^oC=273K
Freezing point of solution=-4.34^oC=(-4.34+273)K
Depression in freezing point=ΔTf=273-(-4.34+273)=0.34K
Kf for water = 1.86 K Kgmol^-1
Since, ΔTf=Kf×m=Kf×wb×1000/Mb×wa
Mb=Kf×wb×1000/wa×ΔTf
Mb=1.86×15×1000/450×0.34=182.35g/mol