Test for ions core practical

• What are flame tests used for?

  To detect and identify ions in samples
• How do instrumental methods of analysis compare to simple chemical tests?

  They are faster, more accurate, and more sensitive
• What is the aim of identifying ions in unknown salts?

  • To identify the ions present
  • Using tests for specified positive and negative ions
• What should you do if given solid salts for testing?

  Dissolve them in distilled water
• What is a precipitate?

  An insoluble substance formed in a reaction
• What is the first step in conducting a flame test?

  Dip a clean wire loop into the sample
• What flame color indicates the presence of lithium ions?

  Red
• What flame color indicates the presence of sodium ions?

  Yellow
• What flame color indicates the presence of potassium ions?

  Lilac
• What flame color indicates the presence of calcium ions?

  Orange-red
• What flame color indicates the presence of copper ions?

  Blue-green
• What are the hydroxide precipitate tests used for?

  • To identify metal ions in solutions
  • By adding dilute sodium hydroxide solution
• What color precipitate indicates the presence of aluminum ions?

  White, dissolves in excess NaOH
• What color precipitate indicates the presence of calcium ions?

  White, no change in excess NaOH
• What color precipitate indicates the presence of copper ions?

  Blue
• What color precipitate indicates the presence of iron(II) ions?

  Green
• What color precipitate indicates the presence of iron(III) ions?

  Brown
• How can you test for ammonium ions?

  • Add dilute sodium hydroxide and warm gently
  • Confirm ammonia gas with damp red litmus paper
• How can you test for carbonate ions?

  • Add dilute hydrochloric acid
  • Confirm with limewater turning milky
• How can you test for sulfate ions?

  • Add dilute hydrochloric acid and barium chloride
  • White precipitate indicates sulfate ions
• How can you test for halide ions?

  • Add dilute nitric acid and silver nitrate
  • Observe precipitate color for identification
• What precipitate color indicates the presence of chloride ions?

  White
• What precipitate color indicates the presence of bromide ions?

  Cream
• What precipitate color indicates the presence of iodide ions?

  Yellow
• What should be included in the results table for ion tests?

  • Salt tested
  • Test conducted
  • Observation made
  • Inference drawn
• How can you identify salt A using test results?

  By analyzing flame color and precipitate
• What is the inference for salt A with a yellow flame?

  Presence of sodium chloride, NaCl
• What is the inference for salt B with a blue precipitate?

  Presence of copper sulfate, CuSO4
• What is the inference for salt C with bubbling and limewater turning milky?

  Presence of ammonium carbonate, (NH4)2CO3
• Why is it difficult to distinguish between dilute solutions of halide ions?

  • Very dilute solutions give faint precipitates
  • Hard to differentiate colors of precipitates
• What precautions should be taken when handling barium chloride?

  • Use only dilute solutions
  • Avoid inhalation and ingestion
• What precautions should be taken when handling silver nitrate?

  • Wear eye protection
  • Avoid skin contact