what is a titration
- form of volumetric analysis
can be used to find
- concentration
- molar mass
- formula
- water of crystallisation
What colours are the two indicators for titration
Phenolthalein is COLOURLESS in acid and pink in alkali
Methyl orange is red in acid and YELLOW in alkali
Rough titration vs Accurate titration
A rough titration is when you add acid to alkali using a burette, giving the flask a regular swirl
- An accurate titration is where you take an initial reading of the acid in the burette, and RUN the acid in to within 2cm^3 of the end point, then once you reach this stage add the acid dropwise.
- Until colour change occurs then STOP immediately
- Repeat this accurate titration a few times until you get 3 concordant results, which can then be used to calculate the mean.
Typical question: “ How can the student make the titration more efficient and accurate”
1) pipette
2) burette
3) appropriate indicator
Titration process in book
1) Using a pipettes measure our a set volume of acid, that you want to find the concentration of, then , pour this into a flask
2) add a few drops of indicator to the flask
3) fill a burette with a standard solution of the acid
4) carefully pour acid into burette using a funnel
- do this below eye level to avoid splashing onto eyes and face. Also wear safety goggles
- we are now ready to carry out a rough/accurate titration
Standard solution of known concentration ( process in book)
1) work out moles of solution (mol=mass/mr)
2) work out mass of solution (mass= moles x mr)
3) weigh a weighing boat with solute, then tip out the solute into a beaker then weigh the empty weighing boat ( which still may contain traces of solute), then subtract the mass of the empty weighing boat from the mass of the weighing boat and solute together, to find the mass of the solute only
4) add distilled water to the beaker and stir to dissolve
5) pour the solution into a volumetric flask using a funnel
6) rinse the beaker and stirring rod, the. Add any solute clinging on to these to the volumetric flask. To ensure nothing is wasted.
7) top up the volumetric flask with distilled water, until the bottom of the meniscus is touching the line
8) turn the flask upside- down a few times to mix
