chem - observations

• Metal Reactions with Acids

  1. Fizzing or effervescence due to the release of hydrogen gas

  2. Heat may be produced

  3. Bubbles of gas are seen, and it can be tested with a lit splint (a 'pop' sound indicates hydrogen)
• Metal Oxides and Carbonates with Acids

  1. Fizzing or effervescence due to the release of carbon dioxide gas

  2. The reaction mixture may become warm
• Hydrogen (H₂)


  A 'pop' sound when a lit splint is introduced
• Oxygen (O₂)


  Relights a glowing splint
• Carbon Dioxide (CO₂)


  Turns limewater milky/cloudy
• Flame Tests for Metal Ions

  • Lithium (Li): Crimson flame
  • Sodium (Na): Yellow flame
  • Potassium (K): Lilac flame
  • Calcium (Ca): Brick-red flame
  • Copper (Cu): Blue-green flame
  • Barium (Ba): Apple-green flame
• Tests for Positive Ions

  1. Ammonium ion (NH₄⁺): Gives off ammonia gas (smells of ammonia) when warmed with sodium hydroxide solution and tested with damp red litmus paper (turns blue)

  2. Carbonate ion (CO₃²⁻): Effervescence with dilute acid, producing carbon dioxide, which turns limewater milky
• Tests for Negative Ions

  1. Chloride ion (Cl⁻): White precipitate with silver nitrate solution (AgNO₃) which is soluble in dilute ammonia solution

  2. Sulfate ion (SO₄²⁻): White precipitate with barium chloride solution (BaCl₂) which is insoluble in dilute hydrochloric acid

  3. Carbonate ion (CO₃²⁻): Effervescence with dilute acid, producing carbon dioxide, which turns limewater milky
• Alkanes


  Combustion produces a clean blue flame
• Alkenes


  Combustion produces a smoky flame
• Alcohols


  Combustion produces a clean blue flame and can be identified by their characteristic smells
• Tests for Functional Groups

  1. Alcohols: React with acidified potassium dichromate (orange to green) or acidified potassium permanganate (purple to colorless)

  2. Carboxylic Acids: React with sodium carbonate to produce effervescence (CO₂)

  3. Aldehydes: React with Fehling's solution to give a brick-red precipitate or with Tollens' reagent to give a silver mirror