Tests for Anions

• What are anions?


  Negatively charged ions
• What tests are covered in the video 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
• How can we test for the presence of carbonates in a solution?

  By bubbling carbon dioxide gas through lime water
• What is the result of bubbling carbon dioxide through lime water?

  The lime water turns cloudy
• What is the procedure to test for carbonates in a sample?

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

  The lime water goes cloudy
• What is the test for sulfates based on?

  The reaction of barium ions with sulfate ions to form barium sulfate
• What is the appearance of barium sulfate when formed?

  It is a white precipitate
• What must be done before adding barium ions to test for sulfates?

  Add dilute hydrochloric acid to remove carbonate or sulfite ions
• Why do we add dilute hydrochloric acid before testing for sulfates?

  To remove impurities that could react with barium ions
• What is the first step in the test for halide ions?

  Add dilute nitric acid to remove carbonate and sulfite impurities
• What is added to the sample to test for halide ions after nitric acid?

  Add silver nitrate
• How does the color of the precipitate help identify halide ions?

  The color indicates which halide ion is present
• What color precipitate forms with chloride ions?

  White precipitate (silver chloride)
• What color precipitate forms with bromide ions?

  Cream precipitate (silver bromide)
• What color precipitate forms with iodide ions?

  Yellow precipitate (silver iodide)
• What are the steps involved in the test for sulfates?

  1. Add dilute hydrochloric acid to remove impurities.
  2. Add barium chloride solution.
  3. Observe for the formation of a white precipitate.
• What are the steps involved in the test for halide ions?

  1. Add dilute nitric acid to remove impurities.
  2. Add silver nitrate solution.
  3. Observe the color of the precipitate to identify the halide ion.
• What are the differences in the tests for sulfates and halide ions?

  • Sulfate test uses dilute hydrochloric acid and barium chloride.
  • Halide test uses dilute nitric acid and silver nitrate.
  • Precipitate colors differ based on the ion present.