VCE Chemistry Question Thread

[sweetiepi]

Hey Guys,

2 quick questions about significant figures: In our calculations, do we carry through with sig.figs rules throughout each step of the process (as this is what VCAA does on the exam reports)?

And, if you leave an answer to a certain amount of sig.figs in a previous part of the question, and you have to use that number for further calculations, does that previously calculated number have to be taken into account when determining how many sig.figs you give for your answer - or is it always just determined off the numbers VCAA gives you?

Thank you!

1) You should really only round off to the appropriate number of sigfigs at the end of your answer, however if decimals are getting excessive, I believe you can do the number of sigfigs required, then add an ellipsis (i.e. 0.203... (3sf)) but always keep the whole number in your calculator

2) I'd always go with the numbers VCAA give you, when trying to determine the amount of sigfigs

[Gogo14]

With q8biii
There is an increase in B, but in the answers it also shows an increase in A at t2
What is happening?
https://imgur.com/a/JYZvJ

[hmdeadas]

Hey all!
So for my chem SAC results i got
UNIT 3 : 72%, 38%
UNIT 4: 60%, 78%, 81%
So what exam mark would i have to get to recieve a 25 study score? I am probably ranked  6th out of 12.
Only concern is that i am getting really bad for my practice exams and do not want to try as this is my worst / bottom subject... only want enough to get a 25.

[Willba99]

Hey all!
So for my chem SAC results i got
UNIT 3 : 72%, 38%
UNIT 4: 60%, 78%, 81%
So what exam mark would i have to get to recieve a 25 study score? I am probably ranked  6th out of 12.
Only concern is that i am getting really bad for my practice exams and do not want to try as this is my worst / bottom subject... only want enough to get a 25.

Hey! You're asking in the wrong place. Try here:
https://atarnotes.com/forum/index.php?topic=138501.0
One the first page, there's a guide to how to predict your own study score. If not, feel free to ask on that thread and someone should help you

[Phenomenol]

With q8biii
There is an increase in B, but in the answers it also shows an increase in A at t2
What is happening?
https://imgur.com/a/JYZvJ

Your're right, they're wrong. The only immediate change is an increase in concentration of B.

They're ALSO wrong with the stoichiometry. It should be 1 NO + 1 Br₂ <-> 1 NOBr₂. (duhh!!!)

I would take the rest of the exam with a grain of salt.

[usernameincorrect]

Hello!

Ive come across some questions about solubility rules and ionic equations in past exam practice papers (2016 e.g.). Do we need to know these for the upcoming exam? I remember learning them in units 1/2 but kind of forgotten them now.

Also, anyone know where to get the most relevant chemistry practice questions for the current study design? Thanks heaps!

[peanut]

Hello!

Ive come across some questions about solubility rules and ionic equations in past exam practice papers (2016 e.g.). Do we need to know these for the upcoming exam? I remember learning them in units 1/2 but kind of forgotten them now.

Also, anyone know where to get the most relevant chemistry practice questions for the current study design? Thanks heaps!

I don't think so, as these are relevant for Gravimetric analysis (which is out of the study design).

[gypsyakhyar]

What's the best way to study up for AOS3 Outcome 3 - Practical Investigation in terms of the exam coming up?
Thanks in advance

[atar.notes.user]

guys do u think if i do all 2017 checkpoints questions i can get a 90/120 in the exam?

ive done 2 prac exams and so far they havent helped me as my content isnt consolidated finely. Throughout the year, checkpoints really helped me

ill obvioulsy do a final timed exam but should i be wasting time with checkpoints or not

[atar.notes.user]

for experimental questions like 'suggest a reason why this value is different to the one in the data book', is saying not conducted at SLC enough to get the mark?

[Syndicate]

for experimental questions like 'suggest a reason why this value is different to the one in the data book', is saying not conducted at SLC enough to get the mark?

I think it's best if you relate it to the experiment as well. So was it conducted at a different temperature, pressure? etc...

[halo]

Hi. Can someone provide a concise explanation of how carbon monoxide poisoning happens for a 2-3 mark question? I don't really know how to explain it clearly

[atar.notes.user]

guys do u think if i do all 2017 checkpoints questions i can get a 90/120 in the exam?

ive done 2 prac exams and so far they havent helped me as my content isnt consolidated finely. Throughout the year, checkpoints really helped me

ill obvioulsy do a final timed exam but should i be wasting time with checkpoints or not

bump

[ardria]

guys do u think if i do all 2017 checkpoints questions i can get a 90/120 in the exam?

ive done 2 prac exams and so far they havent helped me as my content isnt consolidated finely. Throughout the year, checkpoints really helped me

ill obvioulsy do a final timed exam but should i be wasting time with checkpoints or not

Checkpoints questions are almost all just past VCAA questions anyway. If you had to choose between timed full practice exams and Checkpoints, absolutely choose the practice exams in my opinion, because as well as doing past questions you get used to the 'feel' and timing of doing the exam.

To consolidate your knowledge, I suppose you could determine what your weakest topics are after doing a practice exam, then go back to your notes/study guides/textbook to go over those topics and do the textbook questions. You should at least be able to do all the textbook questions as they're merely checking that you've understood the basics.

[VanillaRice]

guys do u think if i do all 2017 checkpoints questions i can get a 90/120 in the exam?

ive done 2 prac exams and so far they havent helped me as my content isnt consolidated finely. Throughout the year, checkpoints really helped me

ill obvioulsy do a final timed exam but should i be wasting time with checkpoints or not

It is not as simple as doing a certain number of questions/exams = a certain mark on the exam. What is really important is being able to understand what you're doing, so you can apply that knowledge in unfamiliar contexts. If you think doing the checkpoints questions will allow you practise the application of your knowledge to answer questions, then do it. If you do a few questions and find that they aren't that useful to you, then don't. Different things work for different people, so it's up to you to find out what works for you I find checkpoints especially useful for focusing on a specific topic (since the topics are all neatly separated).

Hi. Can someone provide a concise explanation of how carbon monoxide poisoning happens for a 2-3 mark question? I don't really know how to explain it clearly

Consider the two equilibria:
\(\ce{haemoglobin + O2 <=> oxyhaemoglobin}\)
\(\ce{haemoglobin + CO <=> carboxyhaemoglobin}\)

Recall that the equilibrium constant (K) for the second reaction is much, much larger than that for the first equation. Therefore, once CO is present in the system, the reaction will dramatically shift to the right. This reduces the amount of haemoglobin on the left side of reaction 2, which hence reduces the amount of haemoglobin on the left side of reaction 1. Reaction 1 will try to compensate for this change, hence reaction 1 will move backward, thereby reducing the amount of oxyhaemoglobin. So, reaction 1 will move to the left, which means low amounts of oxyhaemoglobin, which means no oxygen transport around the body, which results in carbon monoxide poisoning.
In my opinion, these are the main points you should aim to cover.

Hope this helps