Chemical tests

• Method of flame tests

  -Dip the loop of nichrome wire in dilute acid

  
  

  -Hold the wire in the blue flame until no colour change

  
  

  -Dip the loop into solid sample and place it in the edge of the blue flame.
• Colours of ionic metals in flame

  
  

  Li+ -

  Na+ -

  K+ -

  Ca2+ -

  Cu2+ -


  Li+ - Red

  Na+ - Yellow

  K+ - Lilac

  Ca2+ - Orange- Red

  Cu2+ - Blue - Green
• Metal Hydroxide Method


  -Dissolve small amount of substance in water in a test tube

  
  

  -Add a few drops of NaOH solution

  
  

  -Record colour of precipitate formed

  
  

  -Add dilute NaOH solution until it is in excess and record result
• Metal Hydroxide Results


  Copper (II) - Blue precipitate and remains as blue when added in excess

  
  

  Iron (II) - Green precipitate and remains as green when added in excess

  
  

  Iron (III) - Brown precipitate and remains as red - brown when added in excess

  
  

  Magnesium - White precipitate and remains as white when added in excess

  
  

  Aluminium - White precipitate but turns colourless when added in access

  
  

  Zinc - White precipitate but turns colourless when added in access
• Test for Carbonates


  -Add HCL to solid salt

  
  

  -Test any gas that forms by bubbling it through limewater
• Silver Nitrate Halide Test


  -Acidify sample with dilute Nitric acid then add silver nitrate solution

  
  

  -If halide present, different colours for precipitate formed

  
  

  Silver chloride- white

  Silver bromide- yellow

  Silver iodide- yellow
• Test for sulfates


  -Acidify sample with dilute HCL and add few drops of aq barium chloride

  
  

  -HCL added to remove carbonates

  
  

  -If sulfate present then white precipitate of barium sulfate formed