Reading Exercise: Titration

Titration experiments can be used to produce pure salts by reacting acids and alkalis in a very controlled way. A neutralization reaction takes place where acid and alkali react to form the neutral products salt and water.

In a titration, the acid is added to a fixed volume of alkali, for example sodium hydroxide, in a conical flask. A burette is used to slowly drip the acid into the conical flask. The burette is a tall apparatus with a tap at the bottom that controls the flow of the acid (see image above).

A few drops of indicator are added to the alkali, so you can follow the reaction. The end-point is when the indicator changes colour. A single indicator like phenolphthalein is used because it shows only one very obvious colour change and gives you a sharp end-point. Phenolphthalein will change from pink to colorless at the end-point.

To obtain the pure salt, the water needs to be evaporated from the solution after the end of the titration by heating.

In industry, titration is used in many fields not only to produce pure salts, but also to test the amount of acids or alkalis in materials. For example, titration is very common to determine the amount of acids and alkalis in foods like chocolate. The method is also applied by construction companies to investigate the quality of building materials.

Questions

  1. What is produced by a titration experiment?
  2. Which reaction takes place generally during a titration experiment?
  3. Name the tall apparatus used to add the acid to the conical flask with the alkali.
  4. Which indicator can be used to identify the end-point of a titration experiment.
  5. Why is universal indicator not used to identify the end-point?
  6. What are the colours of phenolphthalein in an acid and in an alkali?
  7. What needs to be done after the titration to obtain the pure salt?
  8. Name two uses of titration experiments in industry.

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