A solution consists of 200. g of a nonelectrolytic solute dissolved in 500. g of water. It freezes at -9.30°C. What is the molecular weight of the solute?
The Freezing point of pure water is
Depression in Freezing point is -9.3
Step 1: Calculate the freezing point depression of the solution.
Step 2 : Calculate the molal concentration of the solution using the freezing point depression.
m = (9.3
m = 5.0 molal
Step 3: Calculate the molecular weight of the unknown using the molal concentration.
m= 5.0 molal
- 0 molal = number of moles of solute / 0.500 kg
number of moles of solute = ( 5.0 mol/ kg ) x 0.500 kg
number of moles of solute = 2.5 moles
moles of substance X = mass of X / Molar mass of X
2.5 moles = 200 g / Molar Mass of X
Molar Mass of X = 200 g / 2.5 moles = 80 g/mol