SAC 2MORO HELP: Sources of error with back titration

[sanam]

Hi guys i had my back titration content of nitrogen in fertiliser sac. i got a percentage of 16% nitrogen in the fert but the company claims its 13%. what sources of error in my prac could have resulted in this overestimation ?

[nacho]

Random error:
Undershot the titration (As in, did not add enough HCl, thus your mols determined for the was less than it should have been)
If the leftover is less tahn it should have been:
Then :
= total - leftover
if the leftover is lower than it should have been, then the reacted will be higher than it should have been.
If the reacted is higher than it should have been, then n(NH4) will be higher than it should have been, thus m(N) will be higher, explaining your overestimate.
if you don't understand, try subbin and comparing some values

lol i got 13.5% for this one

[samiira]

•Misreading the volume - at any moment, and due to whatever reason. This can be for example a parallax problem (when someone reads the volume looking at an angle), or error in counting unmarked graduation marks. When reading the volume on the burette scale is not uncommon to read both upper and lower value in different lighting conditions, which can make a difference.

•Using contaminated solutions - for example when two different solutions are transferred using the same pipette and pipette is not rinsed with distilled water in between.

•Not transferring all solid/liquid when preparing samples - it may happen that part of the solid was left on the funnel during transferring it into flask, or it was simply lost. It is also not uncommon to forget to rinse walls of the glassware after solution was transferred - it may happen both to solution pipetted to some vessel, or to titrant that formed droplet on the flask wall and was not rinsed with distilled water. If the pipette is not clean, some of the solution can be left inside in form of drops on the glass.

•Some solids might have been lost during filtration. This would have decreased the calculated percentage of precipitate
•Precipitate might not have been completely dry as we didn’t have an oven to completely evaporate the moisture.
•There could have been weighing errors which could either decrease or increase the calculated percentage.
•Not rinsing the precipitate before drying it- this would lead to overestimation and an increase in calculated percentage precipitate.
•Forming extra precipitate due to the presence of other competing ions can bring overestimation of results as too much of the precipitate will form. Conversely if you form a precipitate that is too low, there will be underestimation as not all of the ions being analysed as not all of the ions being analysed for will remain in the solution.

[lazykid]

lucky you sanam, i worked in a group of 3 and got 8% or 25% nitrogen. FML

[VivaTequila]

We got 13.6%