A 0.0182 g sample of an unknown substance was dissolved in 2.135 g of benzene. The molality of the solution as determined by freezing-point depression was 0.0698. What is the molecular weight of the unknown substance?
1 Answer
Jan 25, 2018
All you need is the mols of the sample and you can get its molar mass.
#"0.0698 mols solute"/cancel"kg solvent" xx 2.135 xx 10^(-3) cancel"kg benzene solvent"#
#= 1.49 xx 10^(-4) "mols sample"#
Thus, the molar mass was
#color(blue)(M) = "0.0182 g"/(1.49 xx 10^(-4) "mols") = color(blue)("122.13 g/mol")#
