Titration (1 Viewer)

[adomad]

How can you improve the accuracy, validity and reliability of a titration??

 

[fayad158]

dont use naoh as a standard base as it is hygroscopic, repeating the experiment and washing out equipment with appropriate liquids eg wash burette with base not water.

 

[iMAN2]

How can you improve the accuracy, validity and reliability of a titration??

HI ADOMAD!!! its Chezza btw

The correct indicator has to be used that is suitable for the range of the acid and based being used.

This neutralisation will be shown at the end point (close to equivalence point)
so less accurate then using a data logger which will measure the equivalence point.

Disadv of using indicator:
- Destructive technique
- Use only two drops as the indicator itself can be acidic or basic.

Washing technique:
Conical flask - wash with distilled water,
Volumetric flask: wash with distilled water, stopper, invert, shake, discard
Pipette-rinse with distilled water, twirling on side and draining from both sides. Repeat with standard solution (base) and discard into waste beaker, making sure none enters pipette filler. Dry outside of pipette with tissues after cleaning.
Burette: Repeat as above (but with filling solution - acid). Drain distilled water and acid through tap as well.
Funnel: rinse with distilled water and then internal volume (of burette) - the acid.

Suitbale primary standard:
- High purity - valid results
- Chemical stability (low reactivity) - does not react violently with water or gasses in the atmosphere
- High solubility
- High molecular weight - minimises weighing errors.
- Non-hygroscopic and non-efflorescent - does not release/absorb water - so doesn't change the concentration (accuracy)
- Chemical formula accurately known

Base: anhydrous sodium carbonate (Na2CO3)
Acid: hydrated oxalic acid (H2C2O4.2H2O)

Unsuitable indicators:
NaOH (hygroscopic; treats with CO2)

For the following the concentration varies with each batch:
HCL
H2SO4
HNO3
H3PO4

Titration indicators to use:
Strong+Strong --> Neutral: Bromothymol blue
S. Acid+W. Base --> Acidic: Methyl Orange
W. Acid+S. Base --> Basic: Phenolphtalein
W. Acid+W. Base --> CAN'T USE. As both are weak they are constantly trying to reach equilibrium (OH and H30+ are always producing so it doesn't completely ionise.


I'll add more later on conducting the experiment itself, there's about 4 pages that i gotta type up lol

 

[adomad]

i just thought of this today, when doing a titration, doesn't the solution in the burette stick to the insides and reduces the titrated volume??



cause then 25 mLs will really be 24.9 mls depending on how sticky the burette is lol... just thought

 

[Pwnage101]

Technically, yes. But using teflon-coated burettes reduces this. And most burettes are calibrated so this error is minimal.

 

[kaz1]

Accuracy : Rinse equipment appropriately
Reliability: Rough titration and repeat