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Chemical Analysis - Coggle Diagram
Chemical Analysis
Purity and Formulations
Pure substance: Only contains 1 compound or element
Formulation: mixture which has been designed for a useful purpose
Fuels, paint, cleaning products, medicines, alloys
Chromatography
Mobile phase
- the solvent that moves through the paper
Stationary phase
- The ink (or other medium) on the paper
Tests for ions
Tests for Cations (positive)
Metal Hydroxide Precipitate Tests
Cu2+
- blue precipitate
Fe2+
- light green precipitate
Fe3+
- reddish brown precipitate
Al3+
- white precipitate
Mg2+
- white precipitate
Ca2+
- white precipitate
Flame tests distinguish
Magnesium
and
Calcium Hydroxide precipitate
:
Mg2+ = no colour
Ca2+ = orange-red
Add excess Sodium Hydroxide solution to separate Aluminium ions:
Aluminium Hydroxide precipitate
dissolves to form a colourless solution
Magnesium
and
Calcium Hydroxide precipitate
stay unchanged
Metal ion + Hydroxide ion -> Metal Hydroxide precipitate
Sodium Hydroxide solution is added to the metal compound to form a precipitate
Tests for Anions (negative)
Carbonate Ions
Pour hydrochloric acid into the sample
If the limewater solution turns cloudy, Carbonate ions are present
CO3 2-
Sulfate Ions
Add a few drops of dilute hydrochloric acid
Add a few drops of barium chloride solution
The sample is acidified first because carbonate ions also form a white precipitate with barium chloride
White precipitate
forms if Sulfate ions are present
SO4 2-
Halide Ions
Add a few drops of nitric acid
Add silver nitrate solution
You can't use hydrochloric acid because the chlorine would give a false negative
The solution must be acidified first because carbonate ions also form a white precipitate with silver nitrate
Chloride
- white
Bromide
- cream
Iodide
- yellow
Instrumental Analysis
Flame Emission Spectroscopy
Coloured light from the flame can be split to produce an emission spectrum
Disadvantages:
requires energy to heat up the metal. This can also destroy the sample
you can only identify ions (not compounds)
Useful for:
water monitoring
(mercury can be traced)
steel industries
(control the amount of trace metals)
forensic crime
(detect toxic metals found in the body
Advantages:
speed
accuracy
sensitivity
Flame Tests
Lithium - Crimson
Sodium - Yellow
Potassium - Lilac
Calcium - Orange-red
Copper - Green
Testing for Gases