Chemistry of the Environment - Topic 10: Water and Its Treatment

Overview of Water

  • Definition: Water is the most abundant compound on Earth and is essential for life, scientific, and industrial purposes.

Tests for Water Presence

  • Test 1: Anhydrous Cobalt(II) Chloride

    • Appearance: Blue when anhydrous
    • Change: Turns pink when water is present, indicating water absorption.

  • Test 2: Anhydrous Copper(II) Sulfate

    • Appearance: White powder when anhydrous
    • Change: Turns blue when water is added, indicating water absorption.

Characteristics of Pure Water

  • Boiling Point: 100°C (may vary due to impurities)
  • Freezing Point: 0°C (may vary due to impurities)
  • Distilled Water: Used in labs for its purity; ensures accurate results.

Observation for Water Purity

  • Melting Point Check: Pure water melts at 0°C.
  • Boiling Point Check: Pure water boils at 100°C.
  • If the melting and boiling points differ, impurities are present.

Natural Water Sources and Their Composition

  • Common Substances:
    • Dissolved oxygen (beneficial for aquatic life)
    • Metal compounds (essential minerals)
    • Plastics and sewage (potentially harmful)
    • Nitrates and phosphates (can cause eutrophication).

Impact of Eutrophication

  • Process: Nitrates and phosphates lead to water deoxygenation, harming aquatic life.

Domestic Water Treatment Process

  1. Sedimentation: Water sits in a tank to allow larger particles and solids to settle.
  2. Filtration: Water passes through filters (sand, gravel) to remove smaller particles.
  3. Carbon Filtration: Activated carbon removes flavors, odors, and some organic compounds.
  4. Chlorination: Chlorine is added to kill harmful microbes, making water safe for consumption.

Fertilizers in Agriculture

  • Purpose: Added to soil/plants for enhanced nutrient intake, growth, and crop yield.
  • Common Types: Ammonium salts and nitrates (provide nitrogen for plant growth).

NPK Fertilizers

  • Components:
    • Nitrogen: Strong green leaf growth
    • Phosphorus: Root development and flowering
    • Potassium: Disease resistance and fruit production.
  • Example: Potassium nitrate is an effective fertilizer because it provides both nitrogen and potassium, essential for growth.

Conclusion

  • Review of water properties, testing, treatment processes, and fertility enhancement in crops through fertilizers as part of the Chemistry of the Environment.