ATAR Notes: Forum
VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: Phenomenol on October 30, 2017, 12:32:25 am
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Hi all,
This took a while, but I've finished writing the trial exam that I promised a few weeks back! Share it with friends if you think it is helpful.
The exam covers the new study design, and should be quite a bit harder than the real VCAA exam (in retrospect I think some of the multiple-choice questions are quite fiendish ::)). Please try it under exam conditions if you can - 15 minutes reading, 150 minutes writing, no notes.
I have also attached full suggested solutions to the exam. Discussion of the questions here is still very much encouraged!
As always I will be happy to help with clarifying anything in the exam/answering individual questions. I will update the pdf ASAP if there are errors in the current version.
Good luck! ;)
v2: Fixed some errors, improved the marking scheme slightly
v3: Found and fixed problems in 3 multi-choice questions! I also now have full suggested solutions to go with this copy of the exam!
v4: Minor corrections as pointed out by gypsyakhyar and VanillaRice
v5: Fixing some numerical answers in the suggested solutions, as pointed out by my students IRL
v6: Fixed Section A Q16 and Section B Q8 b. as pointed out by manishmao
Please make sure you have the latest copy of both the exam and suggested solutions!
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Just skimmed the exam looks so professional ;D
Added to Useful VCE Chemistry Resources!
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awwwww you are toooo kind
I honestly want to hug you so much!
Thank you!!
I am actually speechless of how kind this is, I really hope everyone helps you out when you need and in other times everyone's really kind to you
:) :-* :)
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Just skimmed the exam looks so professional ;D
Added to Useful VCE Chemistry Resources!
Thanks so much :D
awwwww you are toooo kind
I honestly want to hug you so much!
Thank you!!
I am actually speechless of how kind this is, I really hope everyone helps you out when you need and in other times everyone's really kind to you
:) :-* :)
Thank you! You are the one being too kind! I did have some spare time to invest into something like this. (my exams were done a month ago :P)
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I've forgotten most of Chem, but this looks amazing! You could even say...phenomenal ;)
Thanks so much for your wonderful contributions, Phenomenol - they're really appreciated ;D
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Hi all,
Please update to v3 as I fixed some glaring problems with three of the multi-choice questions :)
Also please find attached in the original post the full set of solutions to go with the latest copy of the exam!
8)
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Hi all,
Please update to v3 as I fixed some glaring problems with three of the multi-choice questions :)
Also please find attached in the original post the full set of solutions to go with the latest copy of the exam!
8)
Thank-you so much for this!!! It looks amazing and will be great use to many of chemistry students who come across it - present or future! Thanks again!
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Love this! Do you mind if I promote it? :)
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Love this! Do you mind if I promote it? :)
Go right ahead! (I may still want to fix some small things here and there down the road from the current version, but please do! :) )
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Wait, for short answer question 1d., biogas includes methane right??
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Wait, for short answer question 1d., biogas includes methane right??
Yes. If you wrote "methane" then you should specify the biological source it can be derived from, in order to distinguish it from methane sourced from underground. In the latter case it would not be considered a biofuel.
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Thanks man! You're a legend. Just in Section B: Q1a. Power output, watts aren't a term that's used in the chemistry study design. Might confuse some students, such as myself (needed to do a cheeky google, haha!).
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correction: Q4ai) proper iupac name for aminoethane should be ethanamine
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Question: 2bi) How do we determine if amount refers to volume or mass?
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Question: Q3 Why are we only getting singlets in the proton NMR?
(sorry for spam, this is exam is awesome, just need help haha)
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Correction: Q5a) Solution doesn't include correct units (should be M^-1)
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Question: 2bi) How do we determine if amount refers to volume or mass?
'Amount' usually refers to the number of mole. Mass and volume are usually explicitly specified.
Question: Q3 Why are we only getting singlets in the proton NMR?
(sorry for spam, this is exam is awesome, just need help haha)
Recall low resolution proton NMR - where essentially splitting isn't present. Compare this to high resolution proton NMR, where signal splitting can be present.
Hope this helps :)
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'Amount' usually refers to the number of mole. Mass and volume are usually explicitly specified.
Recall low resolution proton NMR - where essentially splitting isn't present. Compare this to high resolution proton NMR, where signal splitting can be present.
Hope this helps :)
Thanks heaps man, great help! :)
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Thanks heaps man, great help! :)
I'd like to add something to my response RE: singlets on the proton NMR. From looking at the suggested answer, it turns out the question intended that there was no splitting present either way (whether it was high or low resolution). The reason for this is the hydrogen environments in the molecule have no adjacent hydrogen environments, so there is no splitting.
Hope that clears things up :)
@Phenomenol Do you think it would be a good idea to specify explicitly that it is a high resolution proton NMR spectrum?
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I'd like to add something to my response RE: singlets on the proton NMR. From looking at the suggested answer, it turns out the question intended that there was no splitting present either way (whether it was high or low resolution). The reason for this is the hydrogen environments in the molecule have no adjacent hydrogen environments, so there is no splitting.
Rightio, on further inspection it seems I'm an idiot! Hahaha, thanks heaps for your help :)
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Thanks man! You're a legend. Just in Section B: Q1a. Power output, watts aren't a term that's used in the chemistry study design. Might confuse some students, such as myself (needed to do a cheeky google, haha!).
This is very true. I will change the question to "average energy production rate (in MJ/s)".
correction: Q4ai) proper iupac name for aminoethane should be ethanamine
Absolutely! Fixed.
Correction: Q5a) Solution doesn't include correct units (should be M^-1)
Another good find (I was unaware the units for Kc was added to the study design!). Fixed.
@Phenomenol Do you think it would be a good idea to specify explicitly that it is a high resolution proton NMR spectrum?
Indeed it would! Fixed.
Rightio, on further inspection it seems I'm an idiot! Hahaha, thanks heaps for your help :)
Don't be hard on yourself! Haha :P
I think that's everything addressed in the v4 update.
Thanks to both gypsyakhyar and VanillaRice for pointing out the numerous errors. I very much appreciate it!
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For 10a, is the zn cu2+ not touching each other the only valid answer? Can I talk about how cell voltage isn't an indicator of concentration at all? (or am i wrong)
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For MC Q10 can you explain why the carbon dioxide mole is double the mole of ethanoic acid? What's the chemical equation?
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For MC Q10 can you explain why the carbon dioxide mole is double the mole of ethanoic acid? What's the chemical equation?
We can write an equation for the combustion of ethanoic acid as per other organic fuels (such as methane) by balancing C, H and O
Note: CH3COOH = C2H4O2
\(\ce{C2H4O2 + 2O2 -> 2CO2 + 2H2O}\)
Hope this helps :)
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For 10a, is the zn cu2+ not touching each other the only valid answer? Can I talk about how cell voltage isn't an indicator of concentration at all? (or am i wrong)
Funny story - this was what I originally intended the desired response for the question to be, until a student of mine pointed out that the Zn/Cu2+ collisions do not occur at all.
You're right with the fact that concentration does not directly increase the cell voltage in the same way that it has a direct proportion with current. I would probably say that you would still get full marks if you pointed this out, because you ARE applying your knowledge of the chemical principles you have learnt this year :)
Having said that, I am not very familiar with how experimental design questions are marked so I am not 100% sure... but on a good day I would mark that sort of response as correct!
For MC Q10 can you explain why the carbon dioxide mole is double the mole of ethanoic acid? What's the chemical equation?
Following on from VanillaRice's explanation, a quick mental check of the fuel/CO2 ratio is to note that all the carbon in the reactants is in the fuel, and all the carbon in the products is in CO2. So you can determine the fuel/CO2 ratio by balancing the carbons in each (circumventing balancing the entire equation!)
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Hey, for question 16 multi choice, the solutions state that pressure inside a solution calorimeter is varied, and volume inside a solution calorimeter is constant. The solutions also state that the opposite is true for a bomb calorimeter. However, online sources state the direct opposite of this i.e. A bomb calorimeter is referred to as a constant-volume calorimeter and a solution calorimeter is referred to a a constant pressure calorimeter. Why is this? Thanks a lot for the exam by the way.
Source: https://courses.lumenlearning.com/boundless-chemistry/chapter/calorimetry/
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i lost 21 marks whoops 13 on MC ???
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Also isn't higher concentration = greater cell voltage? I thought the E0 values were an indicator of how "out of equilibrium" (i.e. the reaction quotient), so wouldn't a higher concentration of one of the reactants push the system out of equilibrium further and hence drive up the cell voltage.
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I had a look through the exam paper.
Excellent work. I was particularly impressed with your IR/NMR question; I would never have thought of a question that had that perfect balance between challenging and doable.
I'll promote this on VCE DiscussionSpace because it is definitely an excellently written paper.
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Hey, for question 16 multi choice, the solutions state that pressure inside a solution calorimeter is varied, and volume inside a solution calorimeter is constant. The solutions also state that the opposite is true for a bomb calorimeter. However, online sources state the direct opposite of this i.e. A bomb calorimeter is referred to as a constant-volume calorimeter and a solution calorimeter is referred to a a constant pressure calorimeter. Why is this? Thanks a lot for the exam by the way.
Source: https://courses.lumenlearning.com/boundless-chemistry/chapter/calorimetry/
You're absolutely right :/
This is a complete oversight by me. I will also probably need to alter this question to be slightly more applicable to the study design. Will fix ASAP.
i lost 21 marks whoops 13 on MC ???
You did really well! The MC is definitely on the very tough side of things.
Also isn't higher concentration = greater cell voltage? I thought the E0 values were an indicator of how "out of equilibrium" (i.e. the reaction quotient), so wouldn't a higher concentration of one of the reactants push the system out of equilibrium further and hence drive up the cell voltage.
You are right. The cell voltage under non-standard conditons can be calculated from the Nernst equation. It is true that decreasing concentration of product ions/increasing concentration of reactant ions will both lead to increase in cell voltage, however it is worth noting that both relationships are logarithmic.
If the student had provided your reasoning in his hypothesis it would be very sound :)
I had a look through the exam paper.
Excellent work. I was particularly impressed with your IR/NMR question; I would never have thought of a question that had that perfect balance between challenging and doable.
I'll promote this on VCE DiscussionSpace because it is definitely an excellently written paper.
Thanks so much. This paper is still being improved as peer review continues but it is nearly what I envisioned it to be.
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Thanks for the response, Just another question about the glycogen ether linkage question. How do you connect 2900 glucose units with only 2.33*10^4 linkages. I got confused doing it since I assumed there would be 28999 peptide linkages. Is it because the molecule of glycogen is made up of multiple polysaccharide chains interwoven and held together by hydrogen bonds / dispersion forces? I thought glycogen was a single circular outward branching polysaccharide in which every glucose molecule is connected (Like this image) https://www.google.com.au/imgres?imgurl=https://upload.wikimedia.org/wikipedia/commons/thumb/4/47/Glycogen_structure.svg/1200px-Glycogen_structure.svg.png&imgrefurl=https://en.wikipedia.org/wiki/Glycogen&h=1187&w=1200&tbnid=B_WXpV1_c6m_hM:&tbnh=186&tbnw=188&usg=__W4-agyGP2HSH3H4TGFb-Hq4ni2A=&vet=10ahUKEwiJmtW42K7XAhXGKJQKHTECDtoQ_B0ImwEwEw..i&docid=vJnmhV5rCcUMsM&itg=1&sa=X&ved=0ahUKEwiJmtW42K7XAhXGKJQKHTECDtoQ_B0ImwEwEw)
Would multiple glycogen polysaccharide chains count as a single glycogen molecule?Just making sure since there are many VCAA questions where they give you the molar mass of a polysaccharide chain and ask you to find how many units of glucose / how many ether linkages etc. Thanks again and sorry for long post; I'm really engaging with this exam.
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Thanks for the response, Just another question about the glycogen ether linkage question. How do you connect 2900 glucose units with only 2.33*10^4 linkages. I got confused doing it since I assumed there would be 28999 peptide linkages. Is it because the molecule of glycogen is made up of multiple polysaccharide chains interwoven and held together by hydrogen bonds / dispersion forces? I thought glycogen was a single circular outward branching polysaccharide in which every glucose molecule is connected (Like this image) https://www.google.com.au/imgres?imgurl=https://upload.wikimedia.org/wikipedia/commons/thumb/4/47/Glycogen_structure.svg/1200px-Glycogen_structure.svg.png&imgrefurl=https://en.wikipedia.org/wiki/Glycogen&h=1187&w=1200&tbnid=B_WXpV1_c6m_hM:&tbnh=186&tbnw=188&usg=__W4-agyGP2HSH3H4TGFb-Hq4ni2A=&vet=10ahUKEwiJmtW42K7XAhXGKJQKHTECDtoQ_B0ImwEwEw..i&docid=vJnmhV5rCcUMsM&itg=1&sa=X&ved=0ahUKEwiJmtW42K7XAhXGKJQKHTECDtoQ_B0ImwEwEw)
Would multiple glycogen polysaccharide chains count as a single glycogen molecule?Just making sure since there are many VCAA questions where they give you the molar mass of a polysaccharide chain and ask you to find how many units of glucose / how many ether linkages etc. Thanks again and sorry for long post; I'm really engaging with this exam.
I am happy to help you with your questions!
To be honest, I had not thought about this detail when I chose the numbers for the question. I used this page as a reference for writing the question. But it looks like I have slightly incompatible values - there should in reality be about 13/12 glycosidic linkages per glucose unit (one for every glucose and and a branching link approx. every 12 units apart). I will fix this - thanks again for pointing out another inconsistency!
I believe the entire glycogen structure, including all of its individual chains, would be considered one molecule.
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Hi there! I'm having trouble accessing the file. Would someone be able to send me the link? or post it?
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Hi there! I'm having trouble accessing the file. Would someone be able to send me the link? or post it?
The exam is attached to the first post of this thread. You'll only be able to download it when logged in to your ATAR Notes account. Are you still having issues with it? :)
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All good, I didn’t realise I had to log in to view it, that’s all! What an awesome exam, thank you so much for sharing it with us! 😊
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Hey guys, can someone explain to me why the answer to question 1 isn't D? I thought changing the concentration doesn't change the equilibrium constant
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All good, I didn’t realise I had to log in to view it, that’s all! What an awesome exam, thank you so much for sharing it with us! 😊
I'm glad you liked it!
Hey guys, can someone explain to me why the answer to question 1 isn't D? I thought changing the concentration doesn't change the equilibrium constant
Did you mean to say why the answer isn't B?
While it is true that the equilibrium constant does not change, it does not directly explain why there is no equilibrium shift after time t. After all, there are many examples of when the Kc value does not change but there will be a shift towards reactants or products. This shift arises when the reaction quotient differs from Kc at some point in time.
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Hi there! Thank you for writing this Phenomenol!! :) :) :) Could someone please explain Q18 of the MC questions? Thank you.
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This is a great exam thank you
But question 6 multiple choice the definition of a condensation reaction is that water introduced but this is not shown in the reaction so doesn't this technically mean it is not a condensation reaction?
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Hi I can't seem to find the solutions, could someone please post them again? Thank you!
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OMG THANKYOU KIND STRANGER!! Just finished it. Took half an hour longer though :( :( :(
I feel so sad because I don't want to let myself down in this final, very important, exam.
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Hello :)
I'm really confused with Question 4b, about the two reactions to convert the triglyceride into biodiesel, using ethanol.
1. isn't biodiesal usually a methyl ester, not using ethanol?
2. isn't it one reaction- transesterfercation- to turn the triglyceride to three biodiesel molecules + glycerol? (heinnamann textbook pg 26)
could you please help?
This is the provided answer:
i. Hydrolysis, then condensation (esterification)
ii. H2O (reagent), H2SO4 or H+ (catalyst), glycerol and linolenic acid (products)
iii. H2SO4 or H+ (catalyst), CH3CH2(CH=CHCH2)3(CH2)6COOCH2CH3
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Question 1 from multiple choice has confused me. Since the system cannot partially oppose the change in volume, wouldn't diluting the equilibrium solution also decrease the concentration of MgBr2? Not because we have changed the Equilibrium constant, but because we merely increased the volume of the whole solution??
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"2. isn't it one reaction- transesterfercation- to turn the triglyceride to three biodiesel molecules + glycerol? (heinnamann textbook pg 26)
You are perfectly correct in saying that this reaction is a transesterification. What's tricky about this question is it requires an understanding about the chemical processes that occur during this type of reaction.
First of all in a transesterification reaction we "transform" one ester into another ester. That being we convert our triglycerides, an ester consisting of a glycerol backbone and 3 fatty acid chains, into a methyl ester, our biodiesel molecule. The only way this conversion can occur is if we break our triglyceride into constituent compounds and then react them with another reagent to form the biodiesel molecule - a two step process
The first step is the initial hydrolysis of the triglyceride. We use a strong base like KOH or NaOH to hydrolyse the triglyceride into glycerol and its fatty acid constituents. Next we add methanol to react with the individual fatty acid molecules. These two compounds will undergo a condensation reaction to form our desired biodiesel molecule.
In summary transesterification is actually a two step process involving both hydrolysis and condensation.
Old Ester ---> Fatty Acid + Glycerol ---> New Ester
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Alright, I just got home so I'll answer these questions now.
Hi there! Thank you for writing this Phenomenol!! :) :) :) Could someone please explain Q18 of the MC questions? Thank you.
Here is what I have said in the suggested solutions - I have some further comments afterwards.
Each battery provides 1 V, therefore under standard conditions no reaction occurs in the case of the
Zn(NO3)2 cell as a voltage of at least 1.99 V is required according to the electrochemical series.
Since the reduction of one Ag+ requires one electron, and the reduction of one Cu2+ requires two electrons,
n(Ag) will be double that of n(Cu). And because the molar mass of Ag > molar mass of Cu, the mass of
Ag will also be greater than the mass of Cu. Therefore D is correct.
The premise of this question is that you have the reduction of metal ions to solid metal occurring in each cell, if able.
The reduction reaction will be: Mx+ + xe- -> M, where x is the charge of the metal ion.
The oxidation reaction will be: 2H2O -> O2 + 4H+ + 4e-
The battery must supply a voltage of at least the difference in the reduction half-potentials for this redox reaction to proceed.
In the Ag cell, the required voltage is 0.53 V.
In the Zn cell, the required voltage is 1.99 V.
In the Cu cell, the required voltage is 0.89 V.
So if a 1 V battery is connected to each cell... nothing happens in the second cell! So the mass of Zn deposited is 0.
For the other two cells, you can determine the relative masses of both metals deposited in the same duration by both the amount ratio between electrons/each metal, and the molar mass of each metal.
Hope this helps. If you want further elaboration let me know!
This is a great exam thank you
But question 6 multiple choice the definition of a condensation reaction is that water introduced but this is not shown in the reaction so doesn't this technically mean it is not a condensation reaction?
I'm glad you asked this. A condensation reaction is not defined by the formation of water as a byproduct. A condensation reaction in the strictest sense is a reaction between two functional groups in separate organic compounds, combining to form a larger compound and a small byproduct. In the case of Q6 this small byproduct would be ethanoic acid.
Hi I can't seem to find the solutions, could someone please post them again? Thank you!
Strange. I have attached them again in this post. Let me know if you still can't access it.
OMG THANKYOU KIND STRANGER!! Just finished it. Took half an hour longer though :( :( :(
I feel so sad because I don't want to let myself down in this final, very important, exam.
You're very welcome!
This exam was designed to be pretty hard! Don't worry about it :)
Hello :)
I'm really confused with Question 4b, about the two reactions to convert the triglyceride into biodiesel, using ethanol.
1. isn't biodiesal usually a methyl ester, not using ethanol?
Biodiesel can be either methyl or ethyl esters from what I've gathered. Ethyl esters may be more uncommon.
2. isn't it one reaction- transesterfercation- to turn the triglyceride to three biodiesel molecules + glycerol? (heinnamann textbook pg 26)
I think Iasisdabomb's response is a very good one.
Question 1 from multiple choice has confused me. Since the system cannot partially oppose the change in volume, wouldn't diluting the equilibrium solution also decrease the concentration of MgBr2? Not because we have changed the Equilibrium constant, but because we merely increased the volume of the whole solution??
Ah yes. I have tried to make it clear that I am talking about the change after time t - in other words, not the immediate change at time t, but the gradual change that occurs after. Hope that clarifies things.
Perhaps this question is a bit convoluted :P if enough people complain about it I will do something to fix this.
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Thank you so much Phenomenol!!! :) :) :) :) :) :) :) :) :) :)
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Thank you so much Phenomenol!!! :) :) :) :) :) :) :) :) :) :)
No problem! :)
I wish everyone GOOD LUCK for tomorrow's exam!! I hope you have benefited from the help given on the ATAR Notes forum. Give it your all and don't look back on it!
If you like what you learned this year then I strongly recommend taking a chemistry subject in your first year at uni if convenient :D
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Thanks for this man. It’s very helpful considering there aren’t many practice exams on this study design. 😅
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how do i access it
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how do i access it
Have you tried going to the first post on the first page and downloading the attachments? You can try clicking the link (the blue words with the underline) at the bottom of the first post of this thread, which should either ask permission to download or automatically download the files.
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just discovered this... sooo good... thxxx :D ;D
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Hi all,
This took a while, but I've finished writing the trial exam that I promised a few weeks back! Share it with friends if you think it is helpful.
The exam covers the new study design, and should be quite a bit harder than the real VCAA exam (in retrospect I think some of the multiple-choice questions are quite fiendish ::)). Please try it under exam conditions if you can - 15 minutes reading, 150 minutes writing, no notes.
I have also attached full suggested solutions to the exam. Discussion of the questions here is still very much encouraged!
As always I will be happy to help with clarifying anything in the exam/answering individual questions. I will update the pdf ASAP if there are errors in the current version.
Good luck! ;)
v2: Fixed some errors, improved the marking scheme slightly
v3: Found and fixed problems in 3 multi-choice questions! I also now have full suggested solutions to go with this copy of the exam!
v4: Minor corrections as pointed out by gypsyakhyar and VanillaRice
v5: Fixing some numerical answers in the suggested solutions, as pointed out by my students IRL
v6: Fixed Section A Q16 and Section B Q8 b. as pointed out by manishmao
Please make sure you have the latest copy of both the exam and suggested solutions!
didn't like the exam. Q9 was poorly done and Q8 was even cacca
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didn't like the exam. Q9 was poorly done and Q8 was even cacca
Hey David!
I noticed you comment was fairly negative. The forums here try to be a positive place where people can learn and feel comfortable and stating that questions are poorly written detracts from this environment we try to foster. You can by all means think that a question from this exam is flawed or could be improved - but frame this criticism in a way that someone can learn from. Maybe you think the content assessed in the question is irrelevant - then you can say that you think the question is a bit out of the scope of the study design. This is much better than just calling the question poorly written.
Also consider that this practice exam was voluntarily written by a user here on the forums. It most certainly was a very kind gesture for them to invest the time into creating this practice exam, so it would be nice if kindness was extended back to them when giving feedback. To add to this, when users create resources to share here no one should expect them to be 100% perfect - not even professionally made resources are 100% perfect, so its important to recognize this fact and not harshly judge people for making mistakes.
Don't take this as myself not valuing your input - Everyone's input is welcome - I'm just asking that in future you frame any criticisms more constructively and appreciate the effort people put into creating resources. :)