SAC 1

[appianway]

In volumetric there's also the error caused by the difference between the end point and the equivalence point (they're not always exactly the same), but the indicator used should minimise the effect of this.

[Studyinghard]

Could you say the errors for volumetric analysis when doing the back titration that there wasnt enough NaOH and didnt wash the equipment properly for example the burette with the HCL hence concentration of titre blah blah

[appianway]

You could say that was an error (as it'd definitely affect the concentration of the titre!), but if you were writing about something you did, you wouldn't want to, as it's a huge experimental error which was caused by poor technique.

But if it's out of your control, perhaps.

[Studyinghard]

What about the NaOH. could you say that there wasnt enough NaOH mixed with the fertiliser as such the titre values would be less when titred with the HCL. (This is all if the percentage of Nitrogen ends up being less than the specified amount on the product)

[Blakhitman]

How accurate was everyone's results compared to the stated percentage of the compound on the packet?

This is for gravimetric to find % of Sulphur (as Sulpate) yes?

[TrueTears]

First SAC is just around the corner and was hoping to get some resources regarding this SAC as it is quite a popular one.

We did a gravimetric and a back titration with fertiliser.

We took the fertiliser and dissolved. Then we added HCL and boiled it. We then added barium chloride so that a precipitate of barium sulfate would form.

We also did a back titration when we put ammonium ions and dissolved it. Then added Sodium hydroxide to form ammonia gas and water. then we titrated that with HCL and average titres were done.

Did any schools out there do SACS like these or are there any questions that are available that could come up or just any tips in general I should know about.

Thanks

we had one like this, questions were quite general and tested your knowledge about how you did the prac and stuff

[Blakhitman]

First SAC is just around the corner and was hoping to get some resources regarding this SAC as it is quite a popular one.

We did a gravimetric and a back titration with fertiliser.

We took the fertiliser and dissolved. Then we added HCL and boiled it. We then added barium chloride so that a precipitate of barium sulfate would form.

We also did a back titration when we put ammonium ions and dissolved it. Then added Sodium hydroxide to form ammonia gas and water. then we titrated that with HCL and average titres were done.

Did any schools out there do SACS like these or are there any questions that are available that could come up or just any tips in general I should know about.

Thanks

we had one like this, questions were quite general and tested your knowledge about how you did the prac and stuff

lol do you remember how your results compared to the given % on the fertiliser packet? our whole class got higher for the gravimetric part and the volumetric part....I'm starting to think our teacher read the readings wrong from the packet...

[m@tty]

How accurate was everyone's results compared to the stated percentage of the compound on the packet?

This is for gravimetric to find % of Sulphur (as Sulpate) yes?

I did this one, we used 'Yate's thrive formula' or something. The claim was 13%, I only got 7.88%.... Don't know what went wrong, the experiment seemed to go well. Then I did the calculations, and found this ...

[Studyinghard]

Yeah we had to find content of Sulphur as sulfate and nitrogen as Ammonium.

I got lower percentage then manufacturer for both. For the sulphur which was gravimeteric I wrote that we didnt add enough Barium chloride so enough barium sulfate could be precipitated and then I wrote some of the precipitate could have filtered through because we didnt do coagulation which is a thing to make the particles bigger or something? I also wrote we could have used filter paper with smaller pores.

For the volumetric I got less % aswell as mentioned and I wrote not enough NaOH ( dont think I will get any marks for this ) and the equipemt wasnt washed properly in that burette wasnt rinsed with HCL before titrating (hopefully get some marks for this).