what are sources of error in titration (no human errors)?
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Chem titration meh... watch
- Thread Starter
- 07-03-2018 12:29
- 07-03-2018 13:17
percentage uncertainty = (+-0.5/titre in cm3) x 100
Now looking at the mathematics of the equation, if you use a concentrated solution, you will require a smaller titre, which increases the value of percentage uncertainty which makes the titre less precise. To correct this mistake, you should aim to use a more dilute solution in the burette.
* overshooting. Thought I mention this as its the obvious one - even though its a human error.
* If you are using a pipette to transfer a solution from the beaker to a flask, then there can be errors here. Generally, the best pipette for titration is the volume specific pipette which is graduated with a line for one specific volume. The way its manufactured means you can transfer a specific volume of solution which is very accurate. The plastic pipettes which have multiple graduation marks are the less accurate ones because of the way they are manufactured (i.e. if you transfer 10cm3 according to the pipette then it won't really be 10cm3 it may be above or below but the glass pipettes are very close to 10cm3)
* If you are dissolving an substance into the solvent for the titration. You will first need to measure the mass of the substance you want to dissolve. You can get errors here if you are not using an accurate mass balance (which displays the mass to 3 sig figs). Now, if you are not using the accurate mass balance you can get very large percentage errors in the mass of the substance you are dissolving because their absolute uncertainty is high) refer to point 1.
This can later have an impact on the titre volume, as you may need to use more solution in the burette than you really needed (to fully neutralise or react with the reactants in the flask).
* I'd say this is the most important error - leaving an air tight seal in the tap of the burette. Really when you are preparing the burette there should be no air in the tap (only the solution you want to put in it). If there is an air tight gap, then what will happen is that the obtained titre volume will be greater than the true value - leaving with unreliable and inaccurate results. You can imagine that having an air tight seal will do this as once you open the tap the air will quickly leave the burette causing the burette reading to drop quickly which gives the impression that you used a lot of the solution in the burette.
- Thread Starter
- 08-03-2018 11:32