titrations

Cards (10)

  • titrations are used to...
    find out concentrations
  • what are titrations used for?
    finding out exactly how much acid is needed to neutralise a quantity of alkali - or vice versa
  • titration method
    1) rinse out the burette & pipette using distilled water - ensure every last drop is thoroughly out
    2) write the acid on one beaker and the alkali on the other. pour the acid & alkali into their beakers
    3) fix the metal rod into the clamp stand and attach the clamp holder. slip the burette firmly inside the holder and place the stand on a surface where the top of the burette is at eye level or below. place a ceramic square under the burette and a plastic pot on that. put a funnel in the burette
    4) pour 50cm³ of the acid into the burette & overshoot by 1-2cm³. let the excess acid run out into the pot. remove the funnel & use the laminated piece of paper to ensure the volume of acid is exactly 50cm³
    5) use the pipette filler to fill the pipette with 50cm³ of alkali. add it to the conical flask with some indicator. the alkali should turn pink
    6) carefully, add the acid to the alkali, swirling the conical flask to mix the solutions. as soon as the hydroxide turns colourless, stop adding the acid. use the laminated piece of paper to identify the volume of acid added
    7) record your results and repeat the experiment 4 more times, or until you find 2-3 results that are within 0.2cm³ of each other. calculate an average
    8) repeat the experiment with the average but omit the indicator
  • titration apparatus
    burette, pipette, conical flask, white tile, clamp & stand
  • why should you repeat titrations?
    to find a mean volume
  • to increase the accuracy of your titration and to spot any anomalous results...

    you need several consistent readings
  • rough titration
    a titration carried out to find the approximate value of the end point, but not used in any calculations of the mean titre
  • concordant titres
    A set of titres that vary within a narrow range, usually within 0.10 mL from highest to lowest of one another
  • what kind of indicators are used for titrations?
    single indicators
  • why are single indicators used for titrations?
    you want to be able to see a sudden colour change, which a mixture of different indicators (e.g. universal indicator) will not show