Practical Methods Revision.

I will add to these in future :)

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Method for Dilution.

  • Rinse the pipette with the solution.
  • Pipette _cm^3 of this solution into a _cm^3 volumetric flask and make up to the mark using distilled water.
  • Stopper and invert 3 times.
  • Rinse the pipette with the diluted solution using a pipette filler.
  • Transfer _cm^3 of the diluted solution to a conical flask using a pipette.
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Carrying out a titration.

  • Rinse out a pipette with the solution to go in the conical flask, transfer a known volume of the solution to a conical flask.
  • Add 2 or 3 drops of indicator to the solution. (methyl orange or phenolphthalein-must be named)
  • Rinse the burette with the solution of known concentration and fill up to the 0cm^3 line.
  • Add the solution from the burette into the conical flask until the end point is reached. (state colour change)
  • Repeat for accuracy.
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Flame Tests

Dip a nichrome wire into concentrated hydrochloric acid and then into the solid sample, hold at the edge of a blue bunsen flame. Record flame colour.

K+ - Lilac (pink through cobalt blue glass).

Na+ - Yellow/orange (give one)

Li+ - Crimson

Ca2+ - Brick red

Cu2+ - Blue-green

Ba2+ - Green

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Testing for Halides

Acidify a solution of the salt using nitric acid and silver nitrate solution.

(Add dilute/concentrated ammonia solution to distinguish)

  • Chloride ions will give a white precipitate which is soluble in dilute ammonia solution, and will dissolve to give a colourless solution.
  • Bromide ions will give a cream precipitate which is insoluble in dilute ammonia solution but soluble in concentrated ammonia solution to give a colourless solution.
  • Iodide ions will give a yellow precipitate which is insoluble in both dilute and concentrated ammonia solutions.
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