Aqueous Ions

• What ions can be identified through simple test tube reactions?

  Positive ions and negative ions
• What must be done to solid samples before testing for ions?

  They must be dissolved in deionised water
• Which group of metal ions is tested using barium chloride solution?

  Group 2 metal ions
• What should be added to the test tube after barium chloride solution?

  Dilute sodium hydroxide solution
• What is the purpose of adding sodium hydroxide dropwise to the test tube?

  To ensure it is in excess
• What is the alternative method for testing Group 2 ions mentioned?

  Using ammonia solution and sulfuric acid solution
• What is added to test for ammonium ions?

  A solution containing ammonium ions
• What should be done after adding sodium hydroxide to the ammonium solution?

  Swirl the test tube carefully
• How is the ammonium solution heated during the test?

  Using a water bath above a Bunsen burner
• What color change indicates the presence of ammonia gas?

  Red litmus paper turns blue
• What negative ions can be identified through simple test tube reactions?

  Halide, hydroxide, carbonate, sulfate ions
• What is the first step in testing for halide ions?

  Add the sample to a test tube
• What should be added after the sample in the halide ion test?

  Nitric acid
• What indicates the presence of halide ions when silver nitrate is added?

  A precipitate forms (white, cream, yellow)
• What precipitate forms if chloride ions are present?

  White precipitate (AgCl)
• What precipitate forms if bromide ions are present?

  Cream precipitate (AgBr)
• What precipitate forms if iodide ions are present?

  Yellow precipitate (AgI)
• What is the purpose of further testing halides using ammonia solution?

  To distinguish between silver halide precipitates
• How can hydroxide ions be tested?

  Using red litmus paper or universal indicator
• What indicates the presence of hydroxide ions in a solution?

  Red litmus paper turns blue
• What is added to test for carbonate ions?

  Dilute hydrochloric acid
• What gas is produced when carbonate ions react with hydrochloric acid?

  Carbon dioxide gas
• What happens to limewater when carbon dioxide is bubbled through it?

  It turns milky
• What is the test for sulfate ions?

  Add dilute hydrochloric acid and barium chloride
• What indicates the presence of sulfate ions in a solution?

  A white precipitate of barium sulfate forms
• Why is hydrochloric acid added before testing for sulfate ions?

  To remove any carbonates present
• What is investigated in the reactions of metal-aqua ions?

  Reactions with copper(II), iron(II), iron(III), and aluminium ions
• What should be done after adding sodium hydroxide to metal-aqua ions?

  Shake the test tube and note observations
• Why should the contents of test tubes not be disposed of immediately?

  Some changes take time to observe
• What should be used to describe observations in the reactions of metal-aqua ions?

  Correct vocabulary for solutions and precipitates
• What are the steps for testing for Group 2 metal ions?

  1. Add 10 drops of barium chloride to a test tube.
  2. Add 10 drops of dilute sodium hydroxide.
  3. Swirl to mix and add sodium hydroxide dropwise until in excess.
  4. Repeat for calcium, magnesium, and strontium chloride solutions.
  5. Note observations in a results table.
• What are the steps for testing for ammonium ions?

  1. Add 10 drops of ammonium solution to a test tube.
  2. Add 10 drops of sodium hydroxide.
  3. Swirl to mix.
  4. Heat in a water bath.
  5. Test fumes with damp red litmus paper.
• What are the steps for testing for halide ions?

  1. Add the sample to a test tube.
  2. Add a small amount of nitric acid.
  3. Add a small amount of silver nitrate solution.
  4. Observe for precipitate formation (white, cream, yellow).
• What are the steps for testing for carbonate ions?

  1. Add dilute hydrochloric acid to a test tube.
  2. Add sodium carbonate solution.
  3. Attach a bung with a delivery tube.
  4. Transfer gas to limewater.
  5. Observe if limewater turns milky.
• What are the steps for testing for sulfate ions?

  1. Acidify the sample with dilute hydrochloric acid.
  2. Add a few drops of barium chloride.
  3. Observe for white precipitate of barium sulfate.
• What are the steps for testing metal-aqua ions with bases?

  1. Add 10 drops of metal-aqua ion to a test tube.
  2. Add 10 drops of sodium hydroxide and shake.
  3. Add more sodium hydroxide to excess and note observations.
  4. Repeat with ammonia and sodium carbonate solutions.