5 Questions
What is the vapor pressure of pure hexane at 60 °C?
573 torr
If the freezing point of the solvent is 0 °C, what is 𝚫𝚫𝑻𝑻𝑓𝑓 for a solution with a freezing point of -2 °C?
-2 °C
What is the molality of the sucrose solution formed by adding 10.0 g of sucrose to 100.0 mL of water?
1.00 m
What does 𝚫𝚫𝑻𝑻𝒃𝒃 represent in the context of the freezing point depression equation?
Difference between boiling points of the solution and pure solvent
If a solution has a freezing point depression of -5 °C, what would be the effect on the boiling point of the solution?
No effect on the boiling point
Study Notes
Solution Concentration Units
- Molarity (M): mol/L
- Molality (m): mol/kg
- Mole Fraction (χ): no unit
- Mole Percent (mol %): no unit
- Parts by Mass Percent (%): no unit
- Parts per Million by Mass (ppm): no unit
- Parts per Billion by Mass (ppb): no unit
- Parts by Volume (% or ppm or ppb): no unit
Henry's Law
- Henry's Law Constant (𝒌𝒌𝑯𝑯): M/atm
- Solubility of the gas (𝑺𝑺𝒈𝒈𝒈𝒈𝒈𝒈): M
- Partial pressure of the gas (𝑷𝑷𝒈𝒈𝒈𝒈𝒈𝒈): atm
Colligative Properties
- Colligative properties depend on the amount of solute particles, not the type of particle
- Raoult's Law: 𝑷𝑷𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔 = 𝝌𝝌𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔
- Terms:
- 𝑷𝑷𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔: vapor pressure of the solvent over the solution
- 𝑷𝑷𝒐𝒐𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔: vapor pressure of the pure solvent
- 𝝌𝝌𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔: mole fraction of the solvent
Problem-Solving Strategies
- Skill Builder: Nitrogenated water problem
- Calculate concentration of N2 in water (in M) in a sealed container
- Calculate molarity of N2 in the solution after opening and "going flat"
- Vapor pressure of an aqueous solution with a nonvolatile solute problem
- Calculate mole fraction of solute in the solution
- Ideal solutions: solute-solvent, solute-solute, and solvent-solvent interactions have similar magnitude
Test your understanding of Raoult’s Law by calculating the mole fraction of solute in an aqueous solution with a nonvolatile solute based on vapor pressure data. This quiz is based on Eq 13.4 in a textbook.
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