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Chemistry (5070)

Identification Of Ions And Gases

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Identification Of Ions And Gases

Identification Of Ions And Gases

Ions are atoms that are charged due to loss or gain of ions.
Cations lose electron and have a positive charge.
Anions gain electrons and have a negative charge.

Test For Cations

When you add the cation solution in a sodium hydroxide solution and it gives out a gas that is pungent in smell it is ammonium ion, if it gives a colored precipitate which is blue in color it is copper II ion, if the precipitate is dirty green it is because of iron II ion, for iron III ion the precipitate would be red brown in color. 

If adding the sodium hydroxide solution gives a white precipitate and it is insoluble in excess sodium hydroxide solution it is from Calcium ion. If the white precipitate is soluble in excess sodium hydroxide solution and forms a white precipitate with aqueous ammonia, it will be zinc ion if soluble in excess aqueous ammonia and aluminum ion if insoluble in aqueous ammonia.

Test For Anions

For Carbonate ions, add diluted HCl to the Carbonate solution and this will produce CO2 that turn limewater milky. For chloride and iodide ions, few drops of nitric acid and silver nitrate will produce a dense white precipitate for chloride ions and bright yellow for iodide ions. 

Identification Of Gases

  • Ammonia turns moist red litmus blue.
  • Carbon dioxide turns limewater milky.
  • Chlorine turns blue litmus red and then bleaches it
  • Hydrogen gas gives a pop sound with a lighted wooden splint.
  • Oxygen lights up a glowing wooden splint.
  • Sulfur dioxide turns acidified potassium magnate (VII) solution from purple to colorless.
  • Water turns anhydrous copper II sulfate from white to blue. 
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