Chemistry 3 Analysis and Detection

Revision cards for GCSE Chemistry Unit 3 on Analysis and Detection. It's all the ion tests you need to know for Chemistry 3.

Hope they are useful :)

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Flame Test

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

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Carbonates

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

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Organic Compounds

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.

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Sulphate ions

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.

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Halide ions

To test for halide ions add AgNo3(silver nitrate)

Cl- makes a white precipitate

Br- makes a cream precipitate

I- makes a yellow precipitate

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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.

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Instrumental Methods

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.

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Metal Ions

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

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Comments

Steph Underwood

Fab notes:D... you might want to mention about how zinc carbonate turns white again when cooled?? i dunno but our teacher put quite a bit of emphasis on that:S... But these are great, really useful - Thankk Youu:P 5/5

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