Tests for positive ions

The different tests for positive metal ions: all based on the effect given if you add sodium hydroxide solution drop by drop

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If a coloured precipitate is given

  • If it is light blue, there are copper ions Cu2+present
  • If its green (slowly turning brown) then there are Iron(II) Fe2+ ions present
  • If it is Reddish-Brown then Iron (III)Fe3+ ions are present
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If there is no precipitate

  • Warm solution and test for ammonia
  • If a NH3 smell is given off and the gas turns damp litmus paper blue, then ammonia is present
  • IF no ammonia is detected then it is likely there are no positive metal ions
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White precipitate

  • Add more NaOH solution
  • If the precipitate dissolves, there are aluminium Al 3+ ions present
  • If the precipitate is insoluble, there are calcium Ca 2+ or Magnesium Mg 2+ ions present
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