These ions produce a coloured flame when passed through a bunsen flame.
Li+ (lithium) is makes a crimson flame
K+ (potassium) makes a lilac flame
Ba2+ (barium) makes an apple green flame
Ca2+ (calcium) makes a brick red flame
Na+ (sodium) makes a yellow/orange flame
Carbonates can be tested for by two methods by adding HCl or by thermal decomposition.
When carbonates react with HCl (hydrochloric acid) it turns limewater cloudy because carbon dioxide is present.
This means breaking down with heat. Examples of thermal decomposition in carbonates are copper carbonate and zinc carbonate.
Copper carbonate turns from green to black
Zinc carbonate turns from white to yellow
Organic compounds are things like paper and wood.
When organic compounds are burned in air they char. Char basically means they turn black or ashy.
When organic compunds are tested with bromine water it goes from orange to colourless if a carbon to carbon double bond is present.
A sulphate ion is So42-
There is only one test for sulphate ions.
When BaCl2 is added a white precipiate is formed.
A precipitate is an insolouble salt or solid.
To test for halide ions add AgNo3(silver nitrate)
Cl- makes a white precipitate
Br- makes a cream precipitate
I- makes a yellow precipitate
Ammonia and Nitrates
Nitrates ions NO3-
Add NaOH and Al to the NO3 this produces NH3 and we test for this by turning litmus paper blue. It turns the litmus paper blue because it is an alkali.
Ammonium ions NH4+
Do the same test for nitrates without adding the aluminium. It also makes NH3 and turns litmus paper blue.
Elements can be tested using:
- Mass spectrometry
- AAS - Atomic Absorption Spectometry
Compounds can be tested using:
- Chromatography to separate out
- then spectrometry for detection
- IR infrared. UV ultraviolet. NMR Nuclear Magnetic Resonance.
- Mass spectometry can aso be used
Advantages of instrumental testing are it is quick, reliable and only uses small quantities.
When NaOH is added:
Cu2+ makes a blue precipitate
Fe2+ makes a green precipitate
Fe3+ makes a rusty brown precipitate
Al3+ makes a white precipitate and dissolves with excess NaOH
Ca2+ makes a white precipitate
Mg2+ makes a white precipitate