Solution Chapter 2 Lecture Notes

Homogenous Mixtures

• Homogenous Mixture: A mixture like sugar in water, called a solution.
• Binary Solution: Solution with two components.
  • Solute: e.g., sugar
  • Solvent: e.g., water

Concentration Terms

• Mass Percentage:
  • Formula: ( \text{mass %} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 100 )
  • Example: 10g sugar in 130g solution = ( \frac{10}{130} \times 100 )
• Mole-ity (M):
  • Number of moles of solute in 1 litre of solution.
  • Formula: ( M = \frac{\text{moles of solute}}{\text{volume of solution in litres}} )
  • Note: Depends on temperature (inverse relation with volume)

Molality (m)

• Symbol: Small m
• Moles of solute present in 1 kg of solvent.
• Formula: ( m = \frac{\text{moles of solute}}{\text{mass of solvent in kg}} \times 1000 )

Mole Fraction

• Mole Fraction of A:
  • ( X_A = \frac{\text{moles of A}}{\text{total moles (A+B)}} )
• Total of mole fractions equals 1: ( X_A + X_B = 1 )

Solubility

• Maximum amount of solute that can be dissolved in a specific amount of solvent at a given temperature.
• Saturated Solution: No more solute can dissolve at a certain temperature and pressure.

Thermodynamics in Solutions

• Exothermic Process: Heat is released, decreasing solubility with temperature.
• Endothermic Process: Requires heat, increasing solubility with temperature.

Henry's Law

• Partial pressure of gas in vapor phase is proportional to mole fraction in solution.
• Henry's Constant (kH): Increases with temperature, inversely proportional to solubility.

Raoult's Law

• Applicable to solutions of volatile liquids.
• Law: Partial vapor pressure proportional to mole fraction.
  • Formula: ( P_A = P^0_A X_A )

Ideal Solutions

• Follow Raoult's Law.
• Intermolecular Forces: A-A, B-B, A-B interactions are equal.
• No change in volume or enthalpy upon mixing.

Non-Ideal Solutions

• Do not follow Raoult's Law.
• Positive Deviation: Vapor pressure higher than expected.
• Negative Deviation: Vapor pressure lower than expected.

Azeotropes

• Liquid mixtures which boil at constant temperatures.
• Minimum Azeotropes: Show positive deviation.
• Maximum Azeotropes: Show negative deviation.

Colligative Properties

• Depend on number of solute particles, not nature.
• Relative Lowering of Vapor Pressure
  • ( \text{Lowering} = \text{Mole fraction of solute} )
• Elevation in Boiling Point
  • ( \Delta T_b = K_b \times m )
• Depression in Freezing Point
  • ( \Delta T_f = K_f \times m )

Osmotic Pressure

• Pressure required to stop osmosis.
• Formula: ( \pi = CRT )

Abnormal Molecular Masses

• Molar masses differ from expected values due to association/dissociation.
• Van't Hoff Factor (i): Corrects molecular mass calculations.
  • Dissociation: ( i = 1 + (n-1)\alpha )
  • Association: ( i = 1 + \frac{1}{n-1}\alpha )

Conclusion

• Importance of understanding solution properties and their effects on solubility, boiling/freezing points, and molecular mass calculations.