Anions

• What are anions?

  Negatively charged ions
• What tests are covered for checking the presence of anions?

  • Test for carbonate ions
  • Test for sulfate ions
  • Test for halide ions
• What happens when a carbonate reacts with an acid?

  It forms a salt, carbon dioxide gas, and water
• What is the test for carbonates based on?

  It relies on the formation of carbon dioxide gas
• How do you test for carbonates in a solution?

  Add dilute hydrochloric acid and run the gas through lime water
• What indicates a positive test result for carbonates?

  If the lime water turns cloudy
• What is the test for sulfates based on?

  The reaction of barium ions with sulfate ions to form barium sulfate
• What are the two steps in the sulfate test?

  1. Add dilute hydrochloric acid to remove impurities
  2. Add barium chloride solution to form a white precipitate if sulfates are present
• Why do we add dilute hydrochloric acid before testing for sulfates?

  To remove any carbonate or sulfite ions that could interfere
• What does a white precipitate indicate in the sulfate test?

  That sulfates are present in the sample
• What is the test for halide ions based on?

  The reaction of silver ions with halide ions to form a precipitate
• What are the two steps in the halide test?

  1. Add dilute nitric acid to remove impurities
  2. Add silver nitrate to form a precipitate based on the halide present
• What is the role of dilute nitric acid in the halide test?

  To remove carbonate and sulfite impurities
• What precipitate forms when silver ions react with chloride ions?

  Silver chloride, which is a white precipitate
• What precipitate forms when silver ions react with bromide ions?

  Silver bromide, which is a cream precipitate
• What precipitate forms when silver ions react with iodide ions?

  Silver iodide, which is a yellow precipitate
• How can you determine which halide ion is present in a sample?

  By observing the color of the precipitate formed with silver nitrate
• What is the significance of the color of the precipitate in the halide test?

  • Indicates the specific halide ion present
  • White precipitate: Chloride ion
  • Cream precipitate: Bromide ion
  • Yellow precipitate: Iodide ion
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