XXXPUMPERXXX
Member
shhhh make me believe
-
Best of luck to the class of 2024 for their HSC exams. You got this! Let us know your thoughts on the HSC exams here -
YOU can help the next generation of students in the community! Share your trial papers and notes on our Notes & Resources page
Chemistry Exam Predictions/Thoughts (3 Viewers)
- Thread starter Jojofelyx
- Start date
https://boredofstudies.org/threads/hsc-chemistry-2021-exam-solutions.398134/
For anyone looking for solutions here is my solutions to the exam
For anyone looking for solutions here is my solutions to the exam
should we have known that alkenes can oxidise? Is that part of our syllabus?
It's not explicitly a part of the syllabus. However, the question just asked to identify the compounds so you could've worked it out by elimination
thought it was a mistake so wrote propanoic acid as oxidised
As far as I am aware, the answer to the second question is "no".
Looking at the question without that information, we know that 1-propanol will oxidise with permanganate and will be miscible, so 3 must be 1-propanol. The other miscible compound, 1, must be propanoic acid. You then have two immiscible liquids, hexane and 1-hexene, and you have to guess which of these is oxidisable with permanganate. Given alkanes undergo virtually no reactions beyond combustion and free radical substitution to haloalkanes, the alkene is vastly more likely to be the oxidisable one.
seems very logical however in the test my logic was quite the opposite
It can't be the propanoic acid. This is a polar substance with a short carbon chain and so therefore will be soluble in polar water
That's why number 2 cannot be propanoic acid (disregarding the oxidation stuff)
The hex-1-ene and hexane are the two ones that are insoluble in water as they are non-polar. Alkanes are quite stable and only really undergo two types of reactions (combustion and substitution). Therefore, it will be the alkene which is more electron rich and unstable
I accept that, of course, just as I hope you accept that jazz and my logic as to what the answer is (even ignoring the oxidation issue) is correct.
Life'sHard
Well-Known Member
- Joined
- May 24, 2021
- Messages
- 1,101
- Gender
- Male
- HSC
- 2021
- Uni Grad
- 2025
I would say slightly easier. Because last year the 2019 exam was like pretty easy and then it probably came as a big shock for the 2020 students seeing that exam which was a big step up on the previous year. This one was a little bit easier I would say than the 2020
@Life'sHard, my initial impression matches jazz's.
However, I come at the exam having seen hundreds (maybe even into thousands) of chemistry exams over several HSC syllabi. This exam has questions that I see as part of the natural explorations of the theory that accumulate over years of HSC exams. My biggest surprise was the inclusion of an alkene treated with acidified permanganate. I thought q31 on ammonia was a calculation that I haven't seen at HSC level very often. I thought a spectroscopy question on an amine would be upsetting because they have not appeared in many questions from trials since 2019 - and earlier papers don't cover much of the new syllabus in this area.
Then, after speaking with some of my students and reading comments made here - including comments on what was seen as helpful from the BoS paper - I reflected on how having a new syllabus and the related focus on papers from 2019 onwards means that many current students aren't seeing nearly as much of the variety of questions possible on some topics as is needed. I thought again of how unfortunate it is that the collective past trials available is lacking because the syllabus from 1995 matches much of the content in the new syllabus well, though the style of questions has changed... and yet those papers with many excellent questions are very hard to find.
So, my overall take is this: I think that the 2021 exam will prove to be more difficult than it should have been.
However, I come at the exam having seen hundreds (maybe even into thousands) of chemistry exams over several HSC syllabi. This exam has questions that I see as part of the natural explorations of the theory that accumulate over years of HSC exams. My biggest surprise was the inclusion of an alkene treated with acidified permanganate. I thought q31 on ammonia was a calculation that I haven't seen at HSC level very often. I thought a spectroscopy question on an amine would be upsetting because they have not appeared in many questions from trials since 2019 - and earlier papers don't cover much of the new syllabus in this area.
Then, after speaking with some of my students and reading comments made here - including comments on what was seen as helpful from the BoS paper - I reflected on how having a new syllabus and the related focus on papers from 2019 onwards means that many current students aren't seeing nearly as much of the variety of questions possible on some topics as is needed. I thought again of how unfortunate it is that the collective past trials available is lacking because the syllabus from 1995 matches much of the content in the new syllabus well, though the style of questions has changed... and yet those papers with many excellent questions are very hard to find.
So, my overall take is this: I think that the 2021 exam will prove to be more difficult than it should have been.
icycledough
Well-Known Member
- Joined
- Aug 5, 2021
- Messages
- 784
- Gender
- Male
- HSC
- 2020
What I can notice with this year's exam is that they've definitely put a bigger emphasis on maths calculations in the SAQs ... also looking at this year's exam and my exam last year, I'd say last year's one seems easier.
really? apart from the alkene oxidation which confused me, the only other question which was a pain was the back titration
Hey jazz,
for question 31 I got the same answer, but the final value just doesnt seem like it should work considering that your only looking for a 0.05 molar change in NH3 how would adding 1.3 moles of N2 change NH3 by 0.05 moles.
@tito981, it is because you are trying to increase the amount of ammonia by adding nitrogen only, which means that you are decreasing the amount of hydrogen. As you need the equilibrium constant to be unchanged, you have two factors on the numerator, one increasing and one decreasing, to get the denominator to increase (or maybe the other way around, I don't recall if the question had ammonia as a reactant or product), so the amount of extra nitrogen needed is more than might be expected.
To see what I mean, try increasing the ammonia by a small amount and see by how much the nitrogen and hydrogen decrease when both are changing. Note, however, that changing just the ammonia to see what happens to nitrogen and hydrogen, or changing both nitrogen and hydrogen to get a desired change in ammonia, are both more mathematically advanced problems and would be unlikely to appear in an HSC chemistry exam.
To see what I mean, try increasing the ammonia by a small amount and see by how much the nitrogen and hydrogen decrease when both are changing. Note, however, that changing just the ammonia to see what happens to nitrogen and hydrogen, or changing both nitrogen and hydrogen to get a desired change in ammonia, are both more mathematically advanced problems and would be unlikely to appear in an HSC chemistry exam.
B6 is indeed 82 it seems then
XXXPUMPERXXX
Member
This chemistry exam scaled so good istg half of my booklet was empty and I bullshitted most of the questions i answered still got band 5