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March 28, 2024, 07:07:17 pm

Author Topic: VCE Chemistry Question Thread  (Read 2312951 times)  Share 

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Billuminati

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Re: VCE Chemistry Question Thread
« Reply #9120 on: June 10, 2021, 03:27:29 am »
+4
Hey guys,
Could you have the C=O group of a hydrocarbon (lets say alkane) undergo addition reaction with some other substance, so that the double bonded oxygen is replaced by two elements with single bonds?
Many thanks,
Corey

It certainly can, for example, you can have what’s known as a Grignard reagent (R-MgBr) transferring a carbon chain (the R) to a C=O and generating an alcohol when the C=O bond breaks and the oxygen takes a proton from its surroundings to form an O-H bond. For the purposes of VCE, this isn’t assessable.

I think there might be some conceptual misunderstandings from your post, if an alkane has a C=O, you’re probably looking at a carboxyllic acid, ketone or aldehyde, so it is not technically appropriate to refer to it as an alkane.
« Last Edit: June 10, 2021, 03:46:52 am by Billuminati »
VCE 2016-2018

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Billuminati

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Re: VCE Chemistry Question Thread
« Reply #9121 on: June 10, 2021, 03:43:32 am »
+4
if someone could help with this question

For this question you want to take an ester to an amide. You’ll first want to hydrolyse the ester first (hence A= H2O) to produce propanoic acid and methanol.

Look at your final product. The amide looks like it’s made from propanoic acid which you’ve already generated and methanamine ie CH3NH2.

Then have a look at the methanol (B) you’ve made, it’s only slightly different from methanamine, you just have to swap out the OH for an NH2. To do that, react your methanol with NH3 which should be C.

Now, you have methanamine (D) and propanoic acid (E) which is still in solution. These will react in the presence of a strong acid catalyst and you’ve got your desired product.

I don’t like how they’ve written this question. Technically there should be 2 products (methanol and propanoic acid) in Box B, but they’re focusing on the transformation of methanol.
VCE 2016-2018

2017: Biology [38], Further Maths [44]

2018: Methods [37], French [38], Chem [40], English [44]

UMAT: 56/43/80, 57th percentile (LLLLOOOOOOOOOLLLLLLLL)

ATAR: 98.1

2019-2021: Bachelor of Biomedical Science at Monash (Scholars), minoring in Chemistry

GAMSAT September 2021: 65/67/86, 76 overall (98th percentile)

2022: Chilling

2023+: Transfer to teaching degree

smollbu

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Re: VCE Chemistry Question Thread
« Reply #9122 on: June 13, 2021, 08:16:14 pm »
0
Hello AN! I have an Electrochemical SAC coming up and I'm pretty anxious and need help with some questions I couldn't stop thinking about since my teacher is currently unavailable.


1. In fuel cells, do all the reactants supplied have to be 'fuels?'
2. What is the purpose of a semi-permeable membrane in a cell?
3. Are molten electrolytes more costly than aqueous electrolytes?
4. Would having porous electrodes for fuel cells allow the movement of anions to the anode and cations to the cathode?
5. What are the advantages to having a fuel cell that uses methanol?
6. If an electrolysis question said something like the following, "the electrolyte was an AgNO3 solution" and provided no other details, would we count that as an aqueous solution?
7. Is the anode always the same species as the reductant? And why?
8. What electrolyte is used in the production of aluminium?
9. If for example, we had HCl and its H+ ions were being reduced, would we say that the oxidant is HCl or H+?
10. Why would a theoretical current be lower than the experimental current?




Thank you!!!!!!!

Billuminati

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Re: VCE Chemistry Question Thread
« Reply #9123 on: June 13, 2021, 11:08:06 pm »
+4
Hello AN! I have an Electrochemical SAC coming up and I'm pretty anxious and need help with some questions I couldn't stop thinking about since my teacher is currently unavailable.


1. In fuel cells, do all the reactants supplied have to be 'fuels?'
2. What is the purpose of a semi-permeable membrane in a cell?
3. Are molten electrolytes more costly than aqueous electrolytes?
4. Would having porous electrodes for fuel cells allow the movement of anions to the anode and cations to the cathode?
5. What are the advantages to having a fuel cell that uses methanol?
6. If an electrolysis question said something like the following, "the electrolyte was an AgNO3 solution" and provided no other details, would we count that as an aqueous solution?
7. Is the anode always the same species as the reductant? And why?
8. What electrolyte is used in the production of aluminium?
9. If for example, we had HCl and its H+ ions were being reduced, would we say that the oxidant is HCl or H+?
10. Why would a theoretical current be lower than the experimental current?




Thank you!!!!!!!

I'm going to answer these very quickly without fact checking cuz I have my biochem finals tomorrow, so I apologise if any part of my answer is inaccurate.

1. Remember that you're supplying fuel to the anode, and oxygen is already in the air so you don't need to supply that
2. In electrolytic cells it separates the products at each electrode, in some electrolytic cells that produce fluorine gas, if the products come into contact, they will actually blow up.
3. Yes because you need to heat it and hence you need to pay for the fuel
4. Yes
5. It can potentially be renewable like bioethanol
6. The word "solution" implies an aqueous solution, so you can assume SLC ie 1M.
7. Yes, because oxidation always occur at the anode, and a reductant (or reducing agent) is always the species oxidised during a chemical reaction
8. Molten cryolite
9. Just H+, because the Cl- has dissociated from the H+ and remains in a -1 oxidation state
10. Resistance in wires, solution not at SLC, reaction not 100% efficient ie unreacted reactants or side reactions
VCE 2016-2018

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2022: Chilling

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smollbu

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Re: VCE Chemistry Question Thread
« Reply #9124 on: June 14, 2021, 12:59:21 am »
0
I'm going to answer these very quickly without fact checking cuz I have my biochem finals tomorrow, so I apologise if any part of my answer is inaccurate.

1. Remember that you're supplying fuel to the anode, and oxygen is already in the air so you don't need to supply that
2. In electrolytic cells it separates the products at each electrode, in some electrolytic cells that produce fluorine gas, if the products come into contact, they will actually blow up.
3. Yes because you need to heat it and hence you need to pay for the fuel
4. Yes
5. It can potentially be renewable like bioethanol
6. The word "solution" implies an aqueous solution, so you can assume SLC ie 1M.
7. Yes, because oxidation always occur at the anode, and a reductant (or reducing agent) is always the species oxidised during a chemical reaction
8. Molten cryolite
9. Just H+, because the Cl- has dissociated from the H+ and remains in a -1 oxidation state
10. Resistance in wires, solution not at SLC, reaction not 100% efficient ie unreacted reactants or side reactions


Omggg THANK YOU!!!!! And good luck on your finals tomorrow!!!

Corey King

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Re: VCE Chemistry Question Thread
« Reply #9125 on: June 14, 2021, 02:02:34 pm »
+1
It certainly can, for example, you can have what’s known as a Grignard reagent (R-MgBr) transferring a carbon chain (the R) to a C=O and generating an alcohol when the C=O bond breaks and the oxygen takes a proton from its surroundings to form an O-H bond. For the purposes of VCE, this isn’t assessable.

I think there might be some conceptual misunderstandings from your post, if an alkane has a C=O, you’re probably looking at a carboxyllic acid, ketone or aldehyde, so it is not technically appropriate to refer to it as an alkane.

Well that's cool, and makes sense :)
Thanks mam!

caffinatedloz

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Re: VCE Chemistry Question Thread
« Reply #9126 on: June 16, 2021, 10:28:48 am »
+1
Hey guys,
For my experiment poster, my partner and I are looking at percentage yield of aspirin production at different temperatures. Our teacher told us not to worry about whether the reaction is exothermic or endothermic when predicting the impact that increasing the temperature will have as it's not an equilibrium system.

I guess because of that I'm still struggling to conceptualize whether increasing the temperature will affect the percentage yield at all, or if it will only impact the rate of the reaction. I know that when we perform the reaction over a hot bath it will increase the rate of the reaction, but as we're allowing all our reactions to continue until crystallization ceases I don't think that the rate will affect the yield.

I'd really appreciate some guidance.

Billuminati

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Re: VCE Chemistry Question Thread
« Reply #9127 on: June 16, 2021, 07:24:57 pm »
+3
Hey guys,
For my experiment poster, my partner and I are looking at percentage yield of aspirin production at different temperatures. Our teacher told us not to worry about whether the reaction is exothermic or endothermic when predicting the impact that increasing the temperature will have as it's not an equilibrium system.

I guess because of that I'm still struggling to conceptualize whether increasing the temperature will affect the percentage yield at all, or if it will only impact the rate of the reaction. I know that when we perform the reaction over a hot bath it will increase the rate of the reaction, but as we're allowing all our reactions to continue until crystallization ceases I don't think that the rate will affect the yield.

I'd really appreciate some guidance.

If your teacher is assuming an irreversible reaction, then increasing temperature won't affect the percentage yield. I should highlight that if you're reacting an alcohol and a carboxyllic acid directly, the reaction is actually pretty reversible because you have H2O formed and you know that an ester can be hydrolysed (using H2O) to form the alcohol and acid again.
« Last Edit: June 16, 2021, 07:28:05 pm by Billuminati »
VCE 2016-2018

2017: Biology [38], Further Maths [44]

2018: Methods [37], French [38], Chem [40], English [44]

UMAT: 56/43/80, 57th percentile (LLLLOOOOOOOOOLLLLLLLL)

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2019-2021: Bachelor of Biomedical Science at Monash (Scholars), minoring in Chemistry

GAMSAT September 2021: 65/67/86, 76 overall (98th percentile)

2022: Chilling

2023+: Transfer to teaching degree

caffinatedloz

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Re: VCE Chemistry Question Thread
« Reply #9128 on: June 16, 2021, 09:13:55 pm »
0

Chocolatepistachio

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Re: VCE Chemistry Question Thread
« Reply #9129 on: June 19, 2021, 05:12:52 pm »
0
If someone could help with this question  I don’t understand how to draw conformers
Draw the most stable conformer of 1-propanol as a Newman projection, viewed looking down the c1-c2 bond. Referring to your diagram explain why this conformer is the most stable

sweetcheeks

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Re: VCE Chemistry Question Thread
« Reply #9130 on: June 19, 2021, 07:30:41 pm »
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If someone could help with this question  I don’t understand how to draw conformers
Draw the most stable conformer of 1-propanol as a Newman projection, viewed looking down the c1-c2 bond. Referring to your diagram explain why this conformer is the most stable

Where does this question come from? This is a first year university chemistry type of question and not something to worry about for VCE.

Billuminati

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Re: VCE Chemistry Question Thread
« Reply #9131 on: June 20, 2021, 02:21:18 am »
+2
If someone could help with this question  I don’t understand how to draw conformers
Draw the most stable conformer of 1-propanol as a Newman projection, viewed looking down the c1-c2 bond. Referring to your diagram explain why this conformer is the most stable

Newman Projections aren’t assessed in VCE, you don’t need to know this, but if you’re curious, the staggered conformation is more stable than the eclipsed conformation because electron repulsion in the eclipsed conformation due to the overlap increases its energy and hence decreases its stability.
VCE 2016-2018

2017: Biology [38], Further Maths [44]

2018: Methods [37], French [38], Chem [40], English [44]

UMAT: 56/43/80, 57th percentile (LLLLOOOOOOOOOLLLLLLLL)

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2019-2021: Bachelor of Biomedical Science at Monash (Scholars), minoring in Chemistry

GAMSAT September 2021: 65/67/86, 76 overall (98th percentile)

2022: Chilling

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failingenglish

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Re: VCE Chemistry Question Thread
« Reply #9132 on: June 21, 2021, 09:24:56 pm »
0
Do you think i will be able to bring a plastic pocket into the chem exam to put my data book in so that I can highlight half equations (makes it a bit easier for me)? Would there be a reason that I wouldn't be allowed to do this if it is completely transparent?

scientificllama

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Re: VCE Chemistry Question Thread
« Reply #9133 on: June 21, 2021, 10:48:13 pm »
+3
Do you think i will be able to bring a plastic pocket into the chem exam to put my data book in so that I can highlight half equations (makes it a bit easier for me)? Would there be a reason that I wouldn't be allowed to do this if it is completely transparent?

Seems like a no.

Any extra equipment besides the prescribed stuff like pens, pencils, highlighters, rulers & calc; won't be allowed (unless u have stuff to bring in due to special considerations e.g. medication, food etc.). However, for the chem exam, you will be provided with a data book that is able to be highlighted.

Hopefully that helps :)
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caffinatedloz

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Re: VCE Chemistry Question Thread
« Reply #9134 on: June 23, 2021, 02:36:19 pm »
+2
Plenty of people at my school use a clear plastic pocket to put their pens in if they forget to bring a ziploc bag. I'm not sure what the examiners would do if you start highlighting it though...