Titration RP

• A titration is an experimental technique used to find an unknown concentration of an acid or an alkali.
• 1. A pipette to accurately measure a certain volume of acid or alkali (normally 25 cm3)
  2. A conical flask to contain the liquid from the pipette
  3. A burette to add alkali or acid to the the conical flask
  4. A white tile to place the conical flask on

  
• Method

  1. Use the pipette to add 25cm^3 of alkali to a clean conical flask
  2. Add a few drops of indicator and put the conical flask on a white tile
  3. Fill the burette with acid and note the starting volume
  4. Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix
  5. Stop adding the acid when the end-point is reached (when the acid has neutralised the alkali and the indicator changes colour)
  6. Note the final volume and calculate how much acid you added in total
  7. Repeat and calculate a mean.
• Indicators

  When doing a titration, you must place an indicator in the conical flask so that you can tell when the acid has neutralised the alkali. Indicators show this by changing colour as the pH changes from acidic to alkaline.
• It is important to swirl the conical flask as you add the acid from the burette in order to evenly distribute it, and ensure that the colour change occurs as soon as neutralisation takes place.

  It's also important that you place the conical flask on a white tile, so you can more easily see when the colour change takes place.
• Because you always add the indicator to the flask (and not the burette), you may need to use a different indicator, depending on whether it's an alkali or acid in the flask.
• Indicators + their changes

  • Litmus is red in acidic solutions and blue in alkaline solutions
  • Phenolphthalein is colourless in acidic solutions and pink in alkaline solutions
  • Methyl orange in red in acidic solutions and yellow in alkaline solutions