4.3.8

Neutralisation & Titrations 2

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Titrations

Titration is a technique that measures the volumes of acid and alkali solutions that are needed in a neutralisation reaction.

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Method

  1. Measure a precise volume of unknown solution and place it into a conical flask.
  2. Add a couple of drops of your indicator. The flask should be placed on a white tile so you can observe any colour change.
  3. The titre should be added to the burette and the starting point noted.
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Method cont.

  1. The titre should be added slowly to the unknown solution with swirling.
  2. No more titre should be added once the indicator permanently changes colour. This should be done dropwise towards the end.
  3. This is the end-point of the titration and the volume of titre added should be noted.
  4. Repeat these steps until you obtain concordant results.
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Key variables

  • If, for example, we were neutralising an alkali with an acid, titration could be used to calculate the concentration of the alkali if we knew:
    1. The concentration of the acid to be added.
    2. The volume of the alkali.
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Indicators

  • Indicators show the end point of titrations by suddenly changing colour when the solution turns from acidic to alkaline, or alkaline to acidic.
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Choosing an indicator

  • When choosing an indicator, the strength of the acid and alkali must be considered.
  • If both the acid and alkali are strong, suitable indicators would be:
    • Methyl orange (yellow in alkali → red in acid).
    • Phenolphthalein (pink in alkali → colourless in acid).

Jump to other topics

1Atomic Structure

2Chemical Bonding

3Quantitative Chemistry

4Chemical Changes

5Energy Changes

6The Rate & Extent of Chemical Change

7Organic Chemistry

8Chemical Analysis

9Chemistry of the Atmosphere

10Using Resources

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