Question

Calculate the molar mass of a compound that raises the boiling point of water to 100.15oC when 40.5 g of the compound is dissovled in 500 g of water.

and


A mass of 41 g of an unknown nonelectrolyte is dissolved in 429 g naphthalene. The nonelectrolyte lowers naphthalene's freezing point by 7.2 oC. What is the molecular mass of the unknown substance? (Kf = 6.8 oC/mola

Answer 1

#1.
a. delta T = Kb*molality
You know delta T and Kb, solve for molality.
b. Then molality = mols/kg solvent.
You know molality and kg solvent, solve for mols.
c. mols = grams/molar mass. You know mols and grams, solve for molar mass.

#2.
Same kind as #1. Post your work if you get stuck.