CHEM1 titration practical Flashcards
how calculate moles?
moles=mass/Mr
how to calculate concentration?
moles/volume
what is a titration?
Technique where solution of known concentration is used to determine concentration of unknown solution, known solution added fro burette tk a known quantity of unknown solution until reaction is complete.
why is an indicator added to the unknown solution in a titration?
to provide a colour change which will indicate when the reaction is complete
what equipment is needed for a titration?
-conical flask
-burette
-bulb pipette
-volumetric flask
how would you prepare the burette?
- rinse burette with deionised water (to prevent adverse reaction happening by ensuring previous chemicals are not present. drain out all liquid into waste beaker not sink
2.using funnel rinse some solution through burette, including tap and then drain again into waste beaker
3.using funnel fill burette at/below eye level BEYOND 0cm mark
4.open tap and let top of liquid come to within 0-50 marked zone
5.record reading on burette as initial reading (doesn’t have to be 0.00)
how to use a pipette?
- get a conical flask and wash with deionised water and drain
7.rinse pipette with deionised water and allow to drain
- using pipette filler rinse pipette with solution and drain
9.using pipette filler fill pipette with solution above graduation line. slowly release liquid so level drops until BOTTOM OF MINISCUS touches the line
- transfer contents into clean conical flask
11.touch end of pipette onto surface of solution so all of solution is drawn out and the last drop is drawn out by capillary action
how do you add the indicator and why?
- add 2-3 drops into conical flask making sure it does not touch sides of flask. swirl the flask
- only 2-3 drops are indicator is weakly acidic so could affect overall titre
- place conical flask under burette on white tile and dust height of burette so jet just enters neck of conical flask.
how do you read of the burette?
- always ready liquid with eyes at same level
- using piece white paper/white tile behind liquid to assist you
- measure bottom of meniscus-curved surface of water in tube
- if level on a line it is always recorded with 0 in 2nd decimal place and if in-between lines then 5 as dcplace
how do make up a standard solution give full method
1.obtain volumetric flask (wash with deionised water and drain)
2.weigh out needed amount of solid and make note of exact mass
- obtain clean 150cm beaker and place solid in and add 100cm of deionised water
4.wash weighing boat using deionised water inti beaker to ensure entire solid is transferred
- use stirring rod to help solid dissolve, carefully breaking up any lumps of solid with the rod
- when solid has dissolved remove rod , washing it with deionised water into beaker so any solution on rod isn’t lost
- using filter funnel pour solution in volumetric flask and wash beaker out twice using deionised water and add to flask
- wash funnel through with deionised water into flask before removing it
- add deionised water to flask until level rises to GRADUATION mark, if past park must restart, so ass drop-wise near end until bottom of meniscus line
10.put stopper on flash and invert 7 times until liquid is homogenous
11 then solution is trasffered to clean conical flask using pipette
what are concordant results?
at least 2 titres within 0.10cm of each other (always two 2p)
eg average titre 24.90+24.85/2
what colour is the indicator phenolphthalein in acidic and alkaline solutions?
in acidic it is colourless and in alkaline it is pink
what colour is methyl orange in acidic conditions and alkaline solutions?
in acidic it is orange and in alkaline it is yellow
what happens every time you make a measurement with a piece of apparatus? and is there anyway they can be reduced
there is a small margin of error in that measurement due to the apparatus itself eg no balance can measure exact mass but expensive one and precise will to neaarest0.0001g while cheaper is less precise and to 0.1g so errors such as this are known as apparatus error and can not be avoided but can be reduced by using most precise equipment
how to calculate apparatus error for each piece of equipment?
margin of error/quantity measured x100
