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Chemistry Grade 12 Summary

Chemical Properties and Reactions

  • Sulfuric Acid (H₂SO₄): Colorless, dense, corrosive; decomposes via heat, reacts with metals and involves large heat exchanges during dilution.
  • Chemical Reactions: Key equations presented, e.g., C_x + 2H_2O
    ightarrow C_{50} + 5O_{2} + 8H₂O.

Pesticides

  • Types: Classifications include organochlorines (lipid-soluble, long-lasting, toxic) and organophosphates (water-soluble, less persistent).
  • Botanical Pesticides: Derived from plant sources, non-toxic to animals.
  • Examples: Neem leaf, used in various applications against pests.

Herbicides

  • Types: Selective (target specific weeds) or non-selective (kill all plants).
  • Common Groups: Includes chlorophenoxy acids, triazines, glyphosate.

Sodium Carbonate (Washing Soda)

  • Properties: Crystalline solid, hygroscopic, used primarily in glass manufacturing.
  • Solvay Process: Involves a sequence of reactions starting from calcium carbonate to produce sodium carbonate.

Sodium Hydroxide (NaOH)

  • Production: Various electrolysis methods; safety considerations due to corrosiveness.
  • Uses: In cleaning, manufacturing of pulp, paper, and soaps.

Manufacturing Industries in Ethiopia

  • Chemical Industry: Developing, dominated by imports; includes production of glass, cement, and textiles.
  • Glass Production: Involves mixing silica, sodium carbonate, and calcium; forms through melting and shaping processes.

Ceramic Production

  • Definition: Non-metallic, inorganic solids; processes involve molding, densification, and firing.
  • Uses: Art, kitchenware, and engineering applications; ceramics are durable and insulative.

Cement Manufacturing

  • Materials: Primarily limestone and clay; production involves calcination at high temperatures.
  • Processes: Formation of clinker through chemical reactions of calcium and silicon.

Sugar Production

  • Source: Primarily sugarcane; processes include harvesting, juicing, clarifying, and crystallization.

Paper Manufacturing

  • Components: Mixed from wood pulp and additives; involves pulping (mechanical or chemical), bleaching, and sheet formation.

Tanning Processes

  • Traditional vs. Modern: Methods to convert hides into leather; natural vs. mineral tanning techniques.

Food Processing and Preservation

  • Methods: Traditional (drying, salting) and modern (freezing, vacuum-packing).
  • Preservatives: Inorganic (like NaCl) and organic acids to prevent spoilage.

Manufacturing of Ethanol

  • Sources: Fermentation of carbohydrates and catalytic hydration.
  • Local Beverages: Araki is an example of locally produced alcohol; specific fermentation process detailed.

Soap and Detergent Production

  • Saponification: Reaction of fats/oils with bases to produce soap; involves glycerin removal and finishing steps.
  • Detergents: Chemical composition differs from traditional soap, leading to enhanced performance without hardness issues.