Chem 162 Experiment 6 Molar Mass Determination Using Freezing Point Depression P

Question

Chem 162 Experiment 6 Molar Mass Determination Using Freezing Point Depression Pre-Lab Questions 1. Define the term colligative property 2. Suppose the freezing point of a solution of 2.00 g of an unknown molecular substance in 10.00 g of the solvent benzene is measured. If the solution freezes at a temperature of 6.33 C lower than pure benzene itself, calculate the molar mass of the unknown substance . For a given number of moles of solute, why do ionic substances have a larger effect on the freezing and boiling points of solvents than do nonionic substances?

Explanation / Answer

1)

colligative property :

colligative properties are properties of solutions that depend on the ratio of the number of solute particles to the number of solvent molecules in a solution, and not on the nature of the chemical species present.

2)

delta Tf = Kf x m

6.33 = 5.12 x m

m = 1.236

molality = 1.236 m

molality = moles / mass of solvent

1.236 = moles / 0.010

moles of solute = 0.01236

moles = mass / molar mass

0.01236 = 2.00 / molar mass

molar mass of unknown = 162 g/mol

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.