Test for Anions

• What is an anion?

  A negatively charged ion
• The carbonate test relies on the reaction of carbonates with an acid
• When a carbonate reacts with an acid, it forms carbon dioxide gas, water, and a salt.
• What turns lime water cloudy when carbon dioxide gas is bubbled through it?

  Calcium carbonate
• In the carbonate test, dilute hydrochloric acid is added to the sample.
• What indicates a positive result in the carbonate test?

  Lime water turns cloudy
• The sulfate test uses barium ions to form a white precipitate of barium sulfate.
• The white precipitate in the sulfate test indicates the presence of sulfate ions.
• Why is dilute hydrochloric acid added in the sulfate test?

  To remove impurities
• Barium chloride is added in the sulfate test to provide the barium ions needed for the reaction.
• Steps of the sulfate test

  1️⃣ Add dilute hydrochloric acid

  2️⃣ Add barium chloride solution

  3️⃣ Observe for a white precipitate
• What color precipitate is formed when barium ions react with sulfate ions?

  White
• The halide test uses dilute nitric acid to remove carbonates and sulfites.
• Silver nitrate is added in the halide test to react with halide ions.
• Match the halide ion with the color of its precipitate:

  Chloride ↔️ White

  Bromide ↔️ Cream

  Iodide ↔️ Yellow
• What is the color of the precipitate formed when silver ions react with bromide ions?

  Cream
• The silver nitrate test is also known as the halide test.
• Steps of the halide test

  1️⃣ Add dilute nitric acid

  2️⃣ Add silver nitrate solution

  3️⃣ Observe the color of the precipitate
• The halide test can distinguish between chloride, bromide, and iodide ions based on precipitate color.
• What color precipitate is formed when silver ions react with iodide ions?

  Yellow
• In the halide test, silver ions react with halide ions to form a precipitate.