Chapter: Solutions

Introduction

• Almost all body processes occur in liquid solutions.
• In daily life, we rarely encounter pure substances; most are mixtures of two or more pure substances.
• The properties and utility of these mixtures depend on their composition.

Examples

• Alloys:
  • Brass → Mixture of Copper (Cu) and Zinc (Zn)
  • German Silver → Mixture of Copper (Cu), Zinc (Zn), and Nickel (Ni)
  • Bronze → Mixture of Copper (Cu) and Tin (Sn)
• Fluoride in Water:
  • 1 ppm → Prevents tooth decay
  • 1.5 ppm → Causes mottling of teeth
  • High concentration → Poisonous (Sodium fluoride is used in rat poison)
• Intravenous (IV) Injections:
  • Must have salts dissolved in water at specific ionic concentrations matching blood plasma.

Types of Solutions

1. Gaseous Solutions → Gas in Gas (e.g., Air)
2. Liquid Solutions → Gas, Liquid, or Solid in Liquid (e.g., Soft drinks, Vinegar, Saline water)
3. Solid Solutions → Solid in Solid (e.g., Alloys)

Concentration of Solutions

Methods to express solute concentration:

• Mass Percentage (w/w%) = (Mass of Solute / Mass of Solution) × 100
• Volume Percentage (v/v%) = (Volume of Solute / Volume of Solution) × 100
• Mass/Volume Percentage (w/v%) = (Mass of Solute / Volume of Solution) × 100
• Molarity (M) = Moles of Solute / Volume of Solution (L)
• Molality (m) = Moles of Solute / Mass of Solvent (kg)
• Mole Fraction (χ) = Moles of Component / Total Moles of Solution
• Parts Per Million (ppm) = (Mass of Solute / Mass of Solution) × 10⁶

Properties of Solutions

1. Vapour Pressure:

   • The pressure exerted by the vapour of a liquid in equilibrium with its liquid phase.
   • Affected by temperature and solute concentration.

2. Colligative Properties:

   • Depend only on the number of solute particles, not their nature.
   • Includes:
     • Relative Lowering of Vapour Pressure
     • Elevation of Boiling Point
     • Depression of Freezing Point
     • Osmotic Pressure

Laws Related to Solutions

Raoult’s Law:

• The partial vapour pressure of each volatile component in a solution is proportional to its mole fraction.

Ideal and Non-Ideal Solutions:

• Ideal Solution: Obeys Raoult’s Law at all concentrations and temperatures (e.g., benzene + toluene).
• Non-Ideal Solution: Deviates from Raoult’s Law due to intermolecular interactions.

Applications of Solutions in Daily Life

• IV fluids for medical treatments.
• Use of alloys in industries.
• Fluoridation of water to prevent dental issues.
• Osmosis in biological systems.

This summary provides a structured and clear set of notes for the Solutions chapter. Let me know if you need any modifications!