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March 29, 2024, 12:27:20 pm

Author Topic: QCE Chemistry Questions Thread  (Read 31196 times)

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keltingmeith

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Re: QCE Chemistry Questions Thread
« Reply #75 on: September 22, 2020, 08:33:30 pm »
+2

Thank you! :)
I got halfway there so I guess I'm not too bad. But the answer from the textbook said the molarity of HCl was 0.5M. Which is why I'm very confused.

So, I independently went over my answer again, and realised I did make one mistake - the mole ratio of HCl and carbonate above is wrong, so it should be:



But that brings the final answer to 0.2 M (multiply my original answer by 4), not 0.5 M. I disagree with both, because the smallest amount of sig figs we're given is 3, not 1. But yeah, not sure how they get 0.5 M, likely a typo. I also looked up the question on-line and found a bunch of other people answering it, and they all agree with me. So, if you're not willing to trust some random on AN, how about some random on AN + 2 other randoms on the internet ;)

Bri MT

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Re: QCE Chemistry Questions Thread
« Reply #76 on: September 23, 2020, 07:35:24 am »
+1

Thank you! :)
I got halfway there so I guess I'm not too bad. But the answer from the textbook said the molarity of HCl was 0.5M. Which is why I'm very confused.

So, I independently went over my answer again, and realised I did make one mistake - the mole ratio of HCl and carbonate above is wrong, so it should be:



But that brings the final answer to 0.2 M (multiply my original answer by 4), not 0.5 M. I disagree with both, because the smallest amount of sig figs we're given is 3, not 1. But yeah, not sure how they get 0.5 M, likely a typo. I also looked up the question on-line and found a bunch of other people answering it, and they all agree with me. So, if you're not willing to trust some random on AN, how about some random on AN + 2 other randoms on the internet ;)

It's not rare for textbooks to have some mistakes in them.

Highschool doesn't really have the right terminology for it but I had keltingmeith as a "substitute teacher" in 1st year uni chemistry & as his signature says he's been doing a PhD in chemistry - I'd definitely recommend you trust this "random" over the textbook answer.

Declan.B

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Re: QCE Chemistry Questions Thread
« Reply #77 on: September 29, 2020, 12:09:18 pm »
0
Hi,
The QCE syllabus mentions using analytical techniques, including x-ray crystallography to determine the structure of organic molecules. I haven't done much of that in class and have had some difficulty finding questions relevant to this online. Also, the mock exam had no significant question relating to x-ray crystallography in this way.
I'm happy with my knowledge of how x-ray crystallography works, but I'm having trouble finding questions where it is used to predict the structures of organic molecules at a year 12 level.

keltingmeith

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Re: QCE Chemistry Questions Thread
« Reply #78 on: September 29, 2020, 01:00:43 pm »
+2
Hi,
The QCE syllabus mentions using analytical techniques, including x-ray crystallography to determine the structure of organic molecules. I haven't done much of that in class and have had some difficulty finding questions relevant to this online. Also, the mock exam had no significant question relating to x-ray crystallography in this way.
I'm happy with my knowledge of how x-ray crystallography works, but I'm having trouble finding questions where it is used to predict the structures of organic molecules at a year 12 level.


So, I've done x-ray crystallography before. It's hard. And not just the  doing it bit, but the actual trying to use it to find a structure bit. We're talking about requiring to do millions of calculations for a 10 atom asymmetric unit. You won't be expected to predict a structure based on x-ray data - it's just not feasible. I think it's safe to assume you should only need to be able to identify XRD as a potential tool, or maybe to discuss how it works. I think the fact that it's not directly in the sample exams is quite telling of what you can expect from it.

Declan.B

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Re: QCE Chemistry Questions Thread
« Reply #79 on: September 29, 2020, 01:12:17 pm »
+1
So, I've done x-ray crystallography before. It's hard. And not just the  doing it bit, but the actual trying to use it to find a structure bit. We're talking about requiring to do millions of calculations for a 10 atom asymmetric unit. You won't be expected to predict a structure based on x-ray data - it's just not feasible. I think it's safe to assume you should only need to be able to identify XRD as a potential tool, or maybe to discuss how it works. I think the fact that it's not directly in the sample exams is quite telling of what you can expect from it.
Alright, thank you.
It did seem very complex from what I saw online, as is why I was wondering the year 12 applicable parts. Yet, this is what the syllabus stated on it:
"select and use data from analytical techniques, including mass spectrometry,
x-ray crystallography and infrared spectroscopy, to determine the structure of
organic molecules".
Does this seem to be an error on the QCAA's part with the x-ray crystallography component?

keltingmeith

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Re: QCE Chemistry Questions Thread
« Reply #80 on: September 29, 2020, 01:15:42 pm »
+1
Alright, thank you.
It did seem very complex from what I saw online, as is why I was wondering the year 12 applicable parts. Yet, this is what the syllabus stated on it:
"select and use data from analytical techniques, including mass spectrometry,
x-ray crystallography and infrared spectroscopy, to determine the structure of
organic molecules".
Does this seem to be an error on the QCAA's part with the x-ray crystallography component?


I don't know if I'd call it an error - I think they just didn't think it through very well lmao. Usually study designs are made before sample questions, so I think they made the study design, then sat down to write questions and just went, "... fuck, this is harder than I thought it would be".

Declan.B

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Re: QCE Chemistry Questions Thread
« Reply #81 on: September 29, 2020, 01:43:32 pm »
0
I don't know if I'd call it an error - I think they just didn't think it through very well lmao. Usually study designs are made before sample questions, so I think they made the study design, then sat down to write questions and just went, "... fuck, this is harder than I thought it would be".

oh ok, thanks for that

babo

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Re: QCE Chemistry Questions Thread
« Reply #82 on: October 22, 2020, 02:31:45 pm »
0
Hello, i was wondering if we needed to know the structures of nanotubes and how they were made. Also for other molecular machines? as the syllabus is very vague about this. do we need to know about their reactions conditions?

keltingmeith

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Re: QCE Chemistry Questions Thread
« Reply #83 on: October 22, 2020, 03:32:16 pm »
+4
Hello, i was wondering if we needed to know the structures of nanotubes and how they were made. Also for other molecular machines? as the syllabus is very vague about this. do we need to know about their reactions conditions?

Had to double-take when you said molecular machines - that's what my PhD project is on, hahah! So, molecular machines themselves (the thing that won the Nobel prize in 2016) are not on the syllabus, so maybe you're using the term to mean something else? I'm guessing you mean molecular manufacturing? (I know it seems like manufacturing and machines should be interchangeable - but annoyingly, they're not, sorry about that. Though presumably for the purposes of QCE, the assessors probably won't mind)

I'm not an authority on this, and I only know as much as anybody else who has read the syllabus. My understanding of that section is that you don't need to be able to go into a great deal of depth about any of this. You should understand that there are things made by very specifically positioning them in certain ways, and not just by having a bunch jumbled around in solution (eg, proteins are made by attaching amino acids to a solid support, such that the end carboxyl group in the primary structure is not available for bonding, but the end amine group is). I don't think you need to give reaction conditions.

babo

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Re: QCE Chemistry Questions Thread
« Reply #84 on: October 26, 2020, 09:01:59 am »
0
Thanks a lot, i was kind of freaking out about it. i appreciate the clarification!

piperfred

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Re: QCE Chemistry Questions Thread
« Reply #85 on: October 29, 2020, 11:07:15 am »
+3
Hello, i was wondering if we needed to know the structures of nanotubes and how they were made. Also for other molecular machines? as the syllabus is very vague about this. do we need to know about their reactions conditions?

Hi babo!

I'm studying chemistry too, and here's what I have in my notes about molecular machines and nanotubes if it helps! Just a disclaimer that I'm not certain if this is exactly what we need (like every other 2020 chemistry senior in the state), but I'm fairly confident this will put me in pretty good stead in terms of content :)

Be able to broadly define:
Designer chemicals
Nanoparticles
How nanoparticles are produced -- top-down approach and bottom-up approach
Stereospecificity
Host-guest systems and broad uses (used to bind to and remove hazardous substances from the environment)
The orientation effect (e.g. Ribosomes and the molecular machine Rotaxane)

By broadly define I really mean just one or two sentences to give you a rough idea. I'm sure there wouldn't be anything to complex on the exam, maybe just a multiple choice question.

Hope this helps!
Piper
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keltingmeith

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Re: QCE Chemistry Questions Thread
« Reply #86 on: October 29, 2020, 05:09:56 pm »
0
Hi babo!

I'm studying chemistry too, and here's what I have in my notes about molecular machines and nanotubes if it helps! Just a disclaimer that I'm not certain if this is exactly what we need (like every other 2020 chemistry senior in the state), but I'm fairly confident this will put me in pretty good stead in terms of content :)

Be able to broadly define:
Designer chemicals
Nanoparticles
How nanoparticles are produced -- top-down approach and bottom-up approach
Stereospecificity
Host-guest systems and broad uses (used to bind to and remove hazardous substances from the environment)
The orientation effect (e.g. Ribosomes and the molecular machine Rotaxane)

By broadly define I really mean just one or two sentences to give you a rough idea. I'm sure there wouldn't be anything to complex on the exam, maybe just a multiple choice question.

Hope this helps!
Piper

Okay, so like, I'm now really intrigued since you've specifically mentioned rotaxanes. Not saying you're wrong at all - because nobody knows what the hell is going to be on this exam - but am curious if rotaxanes were taught by your teacher or the textbook? It does make sense for the "orientation effect" (which is a fancy term that NOBODY in the field actually uses lmao, classic high school trying to make things complicated) to be assessable, and rotaxanes are an example of using the orientation effect, but still am curious

piperfred

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Re: QCE Chemistry Questions Thread
« Reply #87 on: October 29, 2020, 07:29:35 pm »
+1
Okay, so like, I'm not really intrigued since you've specifically mentioned rotaxanes. Not saying you're wrong at all - because nobody knows what the hell is going to be on this exam - but am curious if rotaxanes were taught by your teacher or the textbook? It does make sense for the "orientation effect" (which is a fancy term that NOBODY in the field actually uses lmao, classic high school trying to make things complicated) to be assessable, and rotaxanes are an example of using the orientation effect, but still am curious

Hiya!

My textbook (QCE Unit 3 and 4 Pearson Chemistry) used rotaxanes as an example of a molecular machine that uses orientation effect.  It was pretty brief, only half a page I think, including information about them mimicking ribosomes and the fact that they're used to produce peptides.

It's funny that you say no one uses the phrase "orientation effect"! I remember there being a multi-choice question on it in the mock and a heap of us being surprised they went into that much detail; that's partly why I've memorised rough details about rotaxanes because I found the mock much more detail-orientated than I expected.
QCE Class of 2020: Literature, French, Maths Methods, SOR, Legal Studies, Chemistry

Aims: ATAR 92+ or 98+
UQ - Advanced Humanities or Advanced Humanities/Law

Loves music!
https://open.spotify.com/user/piper_fred?si=BbcxIL3SRESDkDcVFX7l5A

pamon2

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Re: QCE Chemistry Questions Thread
« Reply #88 on: November 30, 2020, 07:01:25 pm »
0
Hi there!

This is my first ever post, so apologies if I've put this in the wrong place or if I'm lacking in forum etiquette, I'm really quite new to this ^^ However, I really just wanted to ask about data analysis in the sciences. Particularly, how does one thoroughly analyse data in chem, phy and bio (and all other sciences) in order to reach those 20s? + Where can I go to teach myself how to analyse data and would anyone have any online resources they could offer pertaining to this?

I don't think my school properly equipped anyone with the required data analysis skills in Grade 10, so going into Grade 11 no one could get an A in chem :( I'm hoping to work on this before Grade 12.

Thanks in advance,
Paul :)

Bri MT

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Re: QCE Chemistry Questions Thread
« Reply #89 on: December 01, 2020, 08:24:58 am »
+1
Hi there!

This is my first ever post, so apologies if I've put this in the wrong place or if I'm lacking in forum etiquette, I'm really quite new to this ^^ However, I really just wanted to ask about data analysis in the sciences. Particularly, how does one thoroughly analyse data in chem, phy and bio (and all other sciences) in order to reach those 20s? + Where can I go to teach myself how to analyse data and would anyone have any online resources they could offer pertaining to this?

I don't think my school properly equipped anyone with the required data analysis skills in Grade 10, so going into Grade 11 no one could get an A in chem :( I'm hoping to work on this before Grade 12.

Thanks in advance,
Paul :)

Hey,

Welcome to the forums! :)

You might have seen already but I have made a series of articles talking about data test preparation which you might find helpful:
🧬 Biology: https://atarnotes.com/biology-data-test-advice-qce/
🧪 Chemistry: https://atarnotes.com/chemistry-data-test-advice-qce/
🧲 Physics: https://atarnotes.com/physics-data-test-advice-qce/
🧠 Psychology: https://atarnotes.com/psychology-data-test-advice-qce/


Great to hear that you're tackling this early!

If you look at page 25 of the chemistry syllabus you'll see that it has a section on measurement uncertainty and error. Everything in that part you want to become familiar with (and not just for chemistry). The Victorian equivalent of QCAA has a section for their science subjects where they give advice on scientific investigations and measurement in science which you might find useful. Please note that the information on assessment is different across states, but the meaning of uncertainty, accuracy, significant figures etc. is not.

Please feel free to follow up if you have any more questions, comments etc. :)