Experiment 3: Types of Chemical Reactions

Objectives of the Experiment

• Classify chemical reactions based on rearrangement of reactants.
• Identify evidence of chemical reactions.
• Write and balance chemical equations.

Safety Precautions

• Wear gloves, lab coat, and safety shoes.
• Use proper glassware (test tubes, holders, clippers).

Types of Chemical Reactions

1. Combination Reaction

• Definition: Two or more reactants combine to form one product.
• Example: Burning magnesium ribbon in the air.
  • Observation:
    • Combustion produces a bright white light and smoke.
    • Final product: Magnesium oxide (white powder).

2. Replacement Reaction

• Definition: One element replaces another in a compound.
• Example: Copper with silver nitrate.
  • Reaction: Copper replaces silver ions, forming copper(II) nitrate and solid silver.
  • Observations:
    • Light blue solution due to copper ions.
    • Gray precipitate of silver.
• Second Replacement Reaction: Magnesium with hydrochloric acid.
  • Observation:
    • Hydrogen gas evolved.
    • Heat produced (exothermic reaction).

3. Acid-Base Reaction (Neutralization)

• Definition: Acid and base react to produce salt and water.
• Example: Sodium hydroxide (base) with hydrochloric acid.
  • Observation:
    • Use phenolphthalein indicator: colorless in acid, pink in base.
    • Pink color indicates complete neutralization.

4. Precipitation Reaction

• Definition: Mixing two aqueous solutions results in a solid product.
• Example: Hydrochloric acid with silver nitrate.
  • Observation:
    • White cloudy precipitate (silver chloride) formed.
    • Reaction is also a double replacement reaction.

5. Redox Reaction

• Definition: Involves both reduction and oxidation processes.
• Example: Voltaic cell demonstration with zinc and copper electrodes.
  • Observation:
    • Zinc loses electrons (oxidation) and forms zinc ions.
    • Copper ions gain electrons (reduction) and form copper solid.
    • Current flow demonstrated using a multimeter.
  • Setup:
    • Zinc electrode in zinc sulfate solution, copper electrode in copper sulfate solution.
    • Salt bridge connects the two solutions.

Summary

• Different types of chemical reactions were demonstrated with practical experiments.
• Important evidence of reactions was observed, and the principles of balancing chemical equations were emphasized.