Qualitative analysis: tests for ions

• Explain why the test for any ion must be unique:

  • Each ion has unique chemical properties.
  • Specific tests for ions rely on distinct reactions or observations.
  • Unique tests prevent interference from other ions.
  • Ensures accurate identification of individual ions.
• What flame colour is lithium?

  red.
• What flame colour is sodium?

  yellow.
• What flame colour is potassium?

  lilac, purple.
• What flame colour is calcium?

  orange-red.
• What flame colour is copper?

  blue-green.
• What is a mnemonic that helps memorise the flame tests?

  Look, Can Sultan Yell Profoundly Louder Cause Oliver Can't Go!
• What colour forms when aluminium reacts with hydroxide precipitate?

  White then colourless as it redissolves in NAOH (Only for aluminium).
• What colour forms when Calcium reacts with hydroxide precipitate?

  White.
• What colour forms when Copper reacts with hydroxide precipitate?

  Blue.
• What colour forms when Iron(II) reacts with hydroxide precipitate?

  Green.
• What colour forms when Iron(III) reacts with hydroxide precipitate?

  Brown.
• What is the chemical test for Ammonia?

  Sodium hydroxide solution --> ammonia gas given off.

  Ammonia gas can be tested with damp red litmus paper. It will turn red.
• What is the test for carbonate ions when reacting with a Dilute acid?

  carbonate ions + acid --> carbon dioxide + water.
• What is the test for sulfate ions when reacting with a chloride solution?

  Barium ions + sulfate ions --> barium sulfate.
• What is the test for chloride ions when dilute nitric acid is added then a few drops of silver nitrate?

  White.
• What is the test for Bromide ions when dilute nitric acid is added then a few drops of silver nitrate?

  Cream (light yellow).
• What is the test for iodide ions when dilute nitric acid is added then a few drops of silver nitrate?

  Yellow.
• Instrumental methods of analysis are available and these may improve the sensitivity, accuracy and speed of tests.
• Flame photometer data for determining ion concentration:

  • Utilizes a calibration curve to correlate ion concentration with intensity of emitted light.
  • Calibration curve prepared using known standard solutions of varying ion concentrations.
  • Intensity of emitted light from sample solution compared to calibration curve to determine ion concentration.
• Flame photometer data for identifying metal ions:

  • Compares emission spectra of unknown sample with reference spectra of known metal ions.
  • Each metal ion produces characteristic emission lines at specific wavelengths.
  • Matching emission lines in sample to reference data helps identify metal ions present in the sample.