Analysing substances

This is how you would carry out a typical flame test:

1. dip a clean flame test loop in the sample solution

2. hold the flame test loop at the edge of a Bunsen burner flame

3. observe the changed colour of the flame, and decide which metal it indicates

Results

• Lithium compounds -crimson flame
• Sodium compounds - yellow flame
• Potassium compounds - lilac flame
• Calcium compounds - red flame
• Barium compounds - green flame

Precipitate - An insoluble solid formed in a reaction

For the exam you need to know that-

• Aluminium, calcium, magnesium,
• copper(II), iron(II) and iron(III)

-Ions all form precipitates when reacted with sodium hydroxide solution.

Results-Colour of Precipitate.

• Aluminium - White.
• Calcium - White.
• Magnesium - White.
  • When excees sodium hydocide solution is added to aluminium - precipitate dissolves. 
  • To distingish between calcium and magnesium use flame test.
• Copper(II) - Blue.
• Iron(II) - Green.
• Iron(III) - Brown.

Testing for carbonate ions

• They react with dilute acids to produce CO2 and H2O
• CO2 produces a white participate with limewater
  • Which turns limewater cloudy

Testing for halide ions

• A few drops of dilute nitric acid are added to the unknown solution
• A few drops of silver nitrate solution are then added
• It forms a coloured precipitate 
• Which are: 
  • Chloride - White 
  • Bromide - Cream
  • Iodide - Yellow

Testing for sulfate ions

• A few drops of dilute hydrochloric acid are added to the solution
• A few drops of barium chloride solution are then added
• Forms a white precipitate of barium sulfate

• A pipette accurately measures a volume of an alkali. 
• A pipette filler to put solution in pipette. 
• Alkali put in conical flask.
• A few drops of a suitable indicator added to conical flask. 
  • To show when acid and alkali have neutralised - titration complete.
• Acid placed in burette and starting volume noted.
• the tap on burrette is opends slighlty to allow a slow droping of acid into alkali, 
  • when close to nuetralisation-one drop at a time
• Flask is swirled to mix 
• colour change shows correct amount of acids been added to react completely with alkali 
• volume of acid added from the burette is noted. 
• The titration results can then be used to calculate the concentration of the acid or alkali