volumetric equipment
burettes:
preparation
- rinse before use with solution it is to be filled with twice
- fill with a small amount of solution
- tilt so that it is horizontal
- swirl while horizontal so that solution flows out of the top of the burette into a suitable container
- allow solution to also pass through the tap
- repeat twice
- ensure no air gap remains below tap
- no bubbles!!!
usage:
- funnel to put in titrant/analyte
- remove funnel before usage
pipettes
preparation:
- rinse with deionised water
- 2x rinse with solution with which it is to be filled
conical flasks
preparation:
- best case: dry
usage:
- best case: dry
- rinse with DI water
procedures
making standard solution:
- weigh into volumetric flask
- use funnel, then wash funnel
- fill halfway to fully dissolve (swirl)
- invert, then fill fully
- then invert again to ensure homogenisation
- never extract directly from volumetric flask
titration:
- titres should be around 20mL
- accuracy is lowered for low titres
- wasteful (time, resources) for high titres
- always done to 2 dp (
) - construct table with initial volume, end volume, titre
- min 3 concordant titres
- do a preliminary run first, then go accurate
indicators:
- don’t put too much indicator
- always same amount of indicator in each run
- endpoint (colour change) does not equal equivalence point (stoichiometrically equal amounts)