titration

Apparatus:

  • glass pipette - measures a fixed volume accurately, with reduced percentage error compared to the conical flask

  • burette - accurately measures a variable volume

standard solution:

  • a solution of a solute of known and exact concentration

Making a standard solution:

  1. weighing by difference

    1. measure mass of weighing boat and solid

    2. transfer solid to small beaker and re-weigh the weighing boat

    3. subtract mass of weighing boat to determine mass of solid transferred

  2. add enough solvent to just dissolve the solute ( take care not to exceed the volume of the flask)

  3. transfer solution from the beaker to the volumetric flask. Wash funnel and beaker multiple times, adding washings to flask

  4. add solvent until the solution of the meniscus sits on the gradation line

  5. invert several time to ensure its fully mixed

e.g. when making a standard solution, what technique should be used to measure the correct mass of solid

  • weighing by difference

e.g. how do you use the graduation on a volumetric flask to make a solution up to the volume

  • ensure the bottom of the meniscus is on the graduated line

the burette should be rinsed with the same solution that will be used in the burette before a titration

titration results are recorded to 2dp where the second decimal is a 0 or 5

a conical flask is used rather than a beaker so the solution can be swirled without being spilled

  • placed on white tile so the colour change at the end-point is easily seen

a pipette is used instead of a measuring cylinder to measure a volume of standard solution into a conical flask for a titration as it creates a lower percentage error

before beginning a titration, the funnel must be removed and the jet is full and there are no air bubbles when using a burette

end point of titration identified when there is a permanent colour change

concordant results ( within 0.1cm³ of each other) in a titration are used to calculate the mean titre

2-3 drops of indicator

titration calculations:

  • calculate moles of known concentration solution

  • use stoichiometry ( molar ratios of reactants) to determine number of moles of unknown

  • answer the Q ( either volume or concentration of unknown)