Chemistry Solutions and Concentrations

Solutions

• Solutions are homogeneous mixtures of two or more components.
• A binary solution has two components.
• Components include a solute and a solvent.
  • A solid solution has a solid solvent.
  • A liquid solution has a liquid solvent.
  • A gaseous solution has a gaseous solvent.

Molality and Molarity

• Molality (m): Number of moles of solute per kilogram of solvent.
• Molarity (M): Number of moles of solute per liter of solution.

Boiling Point Elevation

• The difference in boiling points of a solution and the pure solvent is called the elevation in boiling point (ΔT_b).
• ΔT_b = K_b * m * i
  • K_b is the molal boiling point elevation constant.
  • m is the molality of the solution.
  • i is the van't Hoff factor (accounts for dissociation or association).

Concentration

• Concentration is the amount of solute in a given amount of solution.
• Mass by volume percentage (w/v): Mass of solute in 100 mL of solution.
• Molality (m): Moles of solute per kilogram of solvent.
• Molarity (M): Moles of solute per liter of solution.

Solubility

• Solubility is the maximum amount of solute that can dissolve in a given amount of solvent at a particular temperature and pressure.
• Saturated solution: Solution where no more solute can dissolve at a specific temperature and pressure.

Henry's Law

• Solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid at a constant temperature.

Raoult's Law

• For a solution of volatile liquids, the partial vapor pressure of each component is directly proportional to its mole fraction.
• P_total = P₁X₁ + P₂X₂

Ideal vs Non-Ideal Solutions

• Ideal solutions obey Raoult's Law over the entire concentration range.
• Non-ideal solutions deviate from Raoult's Law.
• Three types of non-ideal solutions.
  • Positive deviation: Vapor pressure of the solution greater than predicted. IMFs between unlike molecules are weaker than those between like molecules.
  • Negative deviation: Vapor pressure lower than predicted. IMFs between unlike molecules are stronger than those between like molecules.

Azeotropes

• Azeotropes are binary mixtures with a constant boiling point.
• These can not be separated by fractional distillation.
  • Minimum boiling point azeotrope: Solution boils at a lower temperature than either pure component.
  • Maximum boiling point azeotrope: Solution boils at a higher temperature than either pure component.

Colligative Properties

• Colligative properties depend only on the number of solute particles, not their nature.
  • Relative lowering of vapor pressure: p_{solution} / p_{solvent} ∝ mole fraction of the solute.
  • Elevation of boiling point (ΔT_b): ΔT_b = K_b * m * i
  • Depression of freezing point (ΔT_f): ΔT_f = K_f * m * i
    • K_b and K_f are the respective constants.
    • m is molality
    • i is van't Hoff factor
  • Osmotic pressure (π): π = MRT, where M is the molarity of the solution.

Osmosis

• Osmosis is the flow of solvent from a region of higher solvent concentration (lower solute concentration) to a region of lower solvent concentration (higher solute concentration) across a semipermeable membrane.
• Isotonic solutions: same osmotic pressure.
• Hypertonic solutions: higher osmotic pressure than comparison solution
• Hypotonic solutions: lower osmotic pressure than comparison solution.

Abnormal Molar Mass

• Van't Hoff factor (i) corrects for dissociation or association of solute particles in solution.
• i = (normal molar mass) / (observed molar mass)

This quiz covers key concepts related to solutions in chemistry, including molality and molarity, boiling point elevation, and concentration. Test your understanding of the differences between various types of solutions and how to calculate their properties.