Question

Consider that you prepared a solution by mixing 0.17 g solute with 8.26 g of solvent. If you measured that the solution had a molality of 0.157 m, what is the molar mass of the solute? Express your answer numerically to three significant figures.

Answer 1

mass of solute = 0.17 g

mass of solvent = 8.26 g = 0.00826 kg

molality = 0.157m

molality = number of moles of solute/mass of solvent in Kg

number of moles of solute = molality x mass of solvent in Kg

number of moles of solute = 0.157m x 0.00826 Kg

number of moles of solute = 0.001297 moles

number of moles = mass/mola mass

molar mass = mass/number of moles

molar mass = 0.17/0.001297 = 131.07 grams

molar mass of solute = 131.07 grams/mole.

molar mass of solute = 1.31x10^2 gram/mole