Aspirin SAC

[taniiah]

I stuffed up my last Chem SAC so I need to do good in this one.

We did the aspirin sac and have questions on it later this week.

What type of question do they ask? Btw, our aspirin turned into a blob rather than crystals, do you know why this may be the case? It looked like chewing gum. x.x

And how do u prove sulfuric acid acts as a catalyst rather than a reactant.

We're also going to have questions on chemical pathways. Any tips?

Thank you!

[Pandemonium]

make two batches of aspirin, one with conc H2SO4 and one without H2SO4.
make sure they're reacting for the same amount of time and then drop ferric chloride onto both samples.
the drop on the sample without H2SO4 should turn purple (this indicates that the aspirin produced is not pure) whilst the drop on sample reacted with H2SO4 should remain clear.

the theory here is that aspirin will not change colour on contact with ferric chloride. however, phenol and salicylic acid will (to a purple colour). if it changes to a purple colour, we can then assume that the sample that had the H2SO4 reacted faster because it was catalysed by H2SO4.

i think that should be enough. i don't think they'll hound you with 'prove that the H2SO4 was not consumed in the process' or something.

[polky]

I asked Mao the same question, and he said that one could run the products through a HPLC thing or something, get the peaks, then run a pure H2SO4 sample through the same HPLC thing and get the retention time for the H2SO4.  If H2SO4 was the catalyst, it would not have been consumed in the reaction and thus there would be a peak at the retention time of H2SO4 in the first chromatogram.

I hope that makes sense

[Mao]

I asked Mao the same question, and he said that one could run the products through a HPLC thing or something, get the peaks, then run a pure H2SO4 sample through the same HPLC thing and get the retention time for the H2SO4.  If H2SO4 was the catalyst, it would not have been consumed in the reaction and thus there would be a peak at the retention time of H2SO4 in the first chromatogram.

I hope that makes sense

forgot a few things that VCAA might not like [if this made it into the exam]:

1. the chromatograms are ran under the same conditions

2. they both have a "reference" sample inserted [like 5 mL of 1M ethanol into 95mL solution or something], this allows the integration trace at the end to make sense [as they really are just area ratios rather than exact areas, so we need a reference to make sense of it]

3. the peak of H2SO4 must have the same area ratio to our reference material in both chromatograms [and obviously at the same retention time as already mentioned] to confirm that none has been used up

[doboman]

I can halp but feel concerned about the contradiction going on in these boards. I was sure that a maths question was closed due to the fact that it was regarding sacs- while this question, also regarding sacs- is being answerd. And dont tell me your not helping bcause ive read the question and you guys hae pretty much answered the question. Hmmm

[ice_blockie]

I was sure that a maths question was closed due to the fact that it was regarding sacs- while this question, also regarding sacs- is being answerd.

I understand where you are coming from but I don't think what taniiah is asking is a SAC question. If it was, then either her schools has been really lazy and just plagiarised the heinemann workbook questions or been really lax by telling their student what is on the SAC.

So from my point of view, there isn't much to be wary of. This is unlike the maths question since the nature of the SAC is different. If I can remember correctly, for methods it was the application task SAC which included doing a SAC over several days and being able to do part of it at home. Asking how to do them is an absolute no-no

So yeah...

[Mao]

I can halp but feel concerned about the contradiction going on in these boards. I was sure that a maths question was closed due to the fact that it was regarding sacs- while this question, also regarding sacs- is being answerd. And dont tell me your not helping bcause ive read the question and you guys hae pretty much answered the question. Hmmm

i'm sorry, the fact is the case is clearly different.

the advantages I was against had been on people asking questions from their SAC during the SAC period [which run over days], answering these questions undoubtedly impact these people's scores

here, however, the person does not have the SAC questions, and the questions that were asked here were topics of interest rather than answers. I dont exactly know how a procedure would prove sulfuric acid is a catalyst rather than reactant, these are just thoughts spelt out loud. These are also relevant to the course content rather than being test-specific, [and the test-specific question still remains unanswered]

so, I dont see where the contradiction is, and that's without taking into account that assessment in chemistry is vastly different to assessment in mathematics.

[Collin Li]

Well as the moderator of this board, I'm not going to defend the practices in the Maths boards, so I'm not going to defend any accused inconsistencies.