Chemistry 3 Analysis and Detection

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.

HCl

When carbonates react with HCl (hydrochloric acid) it turns limewater cloudy because carbon dioxide is present.

Thermal decomposition

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 BaCl_{2 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

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:

Cu^{2+ makes a blue precipitate}

Fe^{2+ makes a green precipitate}

Fe^{3+ makes a rusty brown precipitate}

Al^{3+ makes a white precipitate and dissolves with excess NaOH}

Ca^{2+ makes a white precipitate}

Mg^{2+ makes a white precipitate}