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July 30, 2021, 05:54:29 am

Author Topic: VCE Chemistry Question Thread  (Read 1584642 times)  Share 

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smollbu

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Re: VCE Chemistry Question Thread
« Reply #9135 on: June 14, 2021, 12:59:21 am »
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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 #9136 on: June 14, 2021, 02:02:34 pm »
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It certainly can, for example, you can have whatís 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 isnít assessable.

I think there might be some conceptual misunderstandings from your post, if an alkane has a C=O, youíre 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!

laura_

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Re: VCE Chemistry Question Thread
« Reply #9137 on: June 16, 2021, 10:28:48 am »
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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.
she/her

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Billuminati

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Re: VCE Chemistry Question Thread
« Reply #9138 on: June 16, 2021, 07:24:57 pm »
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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

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laura_

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Re: VCE Chemistry Question Thread
« Reply #9139 on: June 16, 2021, 09:13:55 pm »
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she/her

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Chocolatepistachio

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Re: VCE Chemistry Question Thread
« Reply #9140 on: June 19, 2021, 05:12:52 pm »
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If someone could help with this question  I donít 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 #9141 on: June 19, 2021, 07:30:41 pm »
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If someone could help with this question  I donít 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 #9142 on: June 20, 2021, 02:21:18 am »
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If someone could help with this question  I donít 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 arenít assessed in VCE, you donít need to know this, but if youíre 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

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

failingenglish

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Re: VCE Chemistry Question Thread
« Reply #9143 on: June 21, 2021, 09:24:56 pm »
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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 #9144 on: June 21, 2021, 10:48:13 pm »
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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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laura_

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Re: VCE Chemistry Question Thread
« Reply #9145 on: June 23, 2021, 02:36:19 pm »
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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...
she/her

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Owlbird83

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Re: VCE Chemistry Question Thread
« Reply #9146 on: June 23, 2021, 03:54:48 pm »
+1
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...

I agree, the examiners always made us leave plastic pockets on the floor we weren't allowed to have them on the desk, so highlighting wouldn't be allowed.
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Chocolatepistachio

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Re: VCE Chemistry Question Thread
« Reply #9147 on: June 23, 2021, 08:44:07 pm »
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Which of the following solutions would have the highest pH?
A 0.150mol-1 solution of barium hydroxide
B 0.150 moL-1 solution of sodium hydroxide
C 0.150 mol-1 solution of sulfuric acid
D 0.150 moL-1 solution of ammonia

Would this be c or would it be a if you do 14-pOH but itís not an acid

Billuminati

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Re: VCE Chemistry Question Thread
« Reply #9148 on: June 23, 2021, 09:11:17 pm »
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Which of the following solutions would have the highest pH?
A 0.150mol-1 solution of barium hydroxide
B 0.150 moL-1 solution of sodium hydroxide
C 0.150 mol-1 solution of sulfuric acid
D 0.150 moL-1 solution of ammonia

Would this be c or would it be a if you do 14-pOH but itís not an acid

This question is no longer examinable for VCE because acid base equilibria ie Ka, Kb, pKa and pKb have been taken out of the course since 2017. You'll need a Ka or Kb value to figure this out. C is incorrect because the acid has the LOWEST pH.
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2018: Methods [37], French [38], Chem [40], English [44]

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

Chocolatepistachio

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Re: VCE Chemistry Question Thread
« Reply #9149 on: June 28, 2021, 08:15:41 pm »
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How do you remember that if delta G is negative the reaction is spontaneous and itís exergonic