anions (QA)

• In qualitative analysis, the test for anions is more complicated than for cations because each anion requires a different set of reagents
• There are five anions to learn in the syllabus: carbonate, chloride, iodide, nitrate, and sulfate
• For carbonate anion:

  • Add any dilute acid
  • Observation: Effervescence (bubbles)
  • Confirm with lime water test: White precipitate formed
• For nitrate anion:

  • Add sodium hydroxide, aluminum foil, and warm
  • Observation: Ammonia gas
  • Test with moist red litmus paper: Turns blue
• For sulfate anion:

  • Add dilute nitric acid, then barium nitrate
  • Observation: White precipitate (barium sulfate)
• For chloride and iodide anions:

  • Add dilute nitric acid, then silver nitrate
  • Observation: White precipitate (chloride), Yellow precipitate (iodide)
• Adding nitric acid before silver nitrate in tests for chloride and iodide helps eliminate carbonate and hydroxide ions that could also form precipitates
• In a flowchart test, if nitric acid produces a gas, it indicates the presence of carbonate anion
• In a flowchart test, a white precipitate with sodium hydroxide indicates the presence of calcium ions
• In a scenario test, analyzing the formation of white precipitates helps identify the presence of specific ions in compounds
• In a scenario test, observing a green precipitate with sodium hydroxide and a gas turning red litmus paper blue indicates the presence of iron II and nitrate ions