Practicals

• Required practical 1 - making up a standard solution

  • Weigh out an accurate mass of a solid in a clean, dry beaker.
  • Add enough distilled water to dissolve a solid, stirring with a glass rod.
  • Transfer the solution with rinsing to a 250cm^3 volumetric flask using a funnel.
  • Rinse the beaker and glass rod with distilled water and add to the volumetric flask.
  • Make up to the mark by adding distilled water until the bottom of the meniscus is on the mark (using a dropper pipette)
  • Stopper the flask and invert to mix thoroughly.

  
• Acid-base titration


  1. Rinse burette with solution

  2. Fill burette

  3. Rinse pipette with solution

  4. Transfer 25cm^3 of solution to conical flask

  5. Add 2-3 drops of indicator

  6. Add solution from burette with constant swirling until indicator changes colour (rough titre)

  7. Repeat titration to get 2 concordant results, adding dropwise near endpoint

  8. Calculate mean titre from concordant results
• Why do you repeat the titration until concordant results?

  To reduce the effect of random error on titration results