viernes, 8 de febrero de 2013

EXPERIMENT n3: Redox Titration


Aim:
To investigate the amount of hydrogen peroxide in commercial oxygenated water.

Background information:
A titration is a reaction of a solution of unknown concentration with a solution of a known concentration for the purpose of finding out more about the unknown solution. So, redox titrations are very used techniques for knowing the concentration of a solution in a substance.
Commercial oxygenated water is a solution of hydrogen peroxide in distilled water with a variable concentration between 3 and 30 %. This concentration is often used in term of volumes.

Materials:
  •        Stand and clamp
  •     Burette
  •     Erlenmeyer
  •      Pipette
  •     100 mL volumetric flask
  •     Potassium permanganate ( KMnO4) 0.05 M
  •     Commercial oxygenated water
  •     Sulfuric acid 2 M

Procedure:
  1. Arrange the burette in the stand with the clamp. Fill the burette with the potassium permanganate solution until level 0, be careful to not leave bubbles in the burette.
  2. Make a solution of commercial oxygenated water taking 10 mL of it and pouring into a 100 mL volumetric flask with distilled water.
  3. Take 25 mL of this solution using the pipette and pour it in the erlenmeyer, then, add 25 mL of 2 M sulphuric acid and 25 mL of distilled water
  4. Titrate the mix (pour the mix) with the potassium permanganate solution until a slightly violet colour appears in the erlenmeyer.
  5. Write down the volume needed and repeat the whole process again to verify the result.
  6. Calculate the hydrogen peroxide concentration of the commercial oxygenated water and compare the result with the one on the commercial bottle.








2 or 3 minutes after finishing the experiment, the purple colour of the titration turned into an orange-brownish colour. Just like we can see on this images:


Bibliography:


Anne Marie Helmenstine (n.d.), Redox Titration Definition, taken from:

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