Login

Welcome, Guest. Please login or register.

March 29, 2024, 05:19:33 am

Author Topic: VCE Chemistry Question Thread  (Read 2313323 times)  Share 

0 Members and 2 Guests are viewing this topic.

Erutepa

  • VIC MVP - 2019
  • Forum Leader
  • ****
  • Posts: 721
  • evenin'
  • Respect: +775
Re: VCE Chemistry Question Thread
« Reply #8175 on: October 16, 2019, 08:23:20 pm »
+4
3. Hm, not exactly my area of expertise. But from the study design and from the databook, you only need to know and focus on alpha-amino acids (or 2-amino acids). Unfortunately, I can't answer this question!
That's right!
We do not need to know about beta-amino acids.
Qualifications
 > Have counted to 227
 > Can draw really good spiders
 > 2 Poet points
 > 6.5 insanipi points
 > 1 Bri MT point

EllingtonFeint

  • Trendsetter
  • **
  • Posts: 153
  • Offering private tutoring ✨
  • Respect: +24
Re: VCE Chemistry Question Thread
« Reply #8176 on: October 16, 2019, 09:25:15 pm »
0
Hello,
More questions; sorry !!
-Do we need to memorise Faraday's laws?
-Is the cathode positive in the secondary cell??
-Actually could sombody please just give me a super quick summary of secondary cells (probably also fuel cells) and which way the recharges and discharges (i.e.just something super basic like the top equation, oxidation (or is it reduction now???) goes L to R on the electrochem series).
-And Electrolytic cells too, please!

Sorry, I am just so unutterably confused about this topic  :-[  and I've watched a bunch of youtube videos and looked through my summary notes and books but I don't get it yet. I think that I've got the Galvanic cells down but the rest of this is just a tangled mess in my head. We had this random period of time where our chemistry teacher left and our classes were covered by CRTs for a while before we got a new teacher and I guess this is one of those topics that suffered immensely :(

Thank you in advance :)

Biology 🌱 [49] |  English [47]

Surviving and Succeeding in Biology:
https://atarnotes.com/forum/index.php?topic=187145.msg1129188

EllingtonFeint

  • Trendsetter
  • **
  • Posts: 153
  • Offering private tutoring ✨
  • Respect: +24
Re: VCE Chemistry Question Thread
« Reply #8177 on: October 16, 2019, 09:42:20 pm »
0
Oh! I forgot to add in attachments of a question (which is part of the above topics) that was causing lots of confusion.
Here it is... (attached, with the answer too)
I have no idea what is going on and would be so appreciative of some help/explanation :)
Biology 🌱 [49] |  English [47]

Surviving and Succeeding in Biology:
https://atarnotes.com/forum/index.php?topic=187145.msg1129188

JR_StudyEd

  • MOTM: MAY 19
  • Forum Obsessive
  • ***
  • Posts: 379
  • Mental health is #1
  • Respect: +171
Re: VCE Chemistry Question Thread
« Reply #8178 on: October 16, 2019, 09:46:44 pm »
-2
-Do we need to memorise Faraday's laws?
Well, the relevant study design dot point says: the application of stoichiometry and Faraday’s Laws to determine amounts of product, current or time for a particular electrolytic process. So you wouldn't need to memorise it as such. Just apply the knowledge of it.
And the two Faraday equations are in the data booklet! Yay! (They're on page 5 I believe, under chemical relationships, electric charge and number of moles of electrons)

Quote
-Is the cathode positive in the secondary cell??
Yes. The only time it would be negative is if it's an electrolytic cell.

At the moment, that's all I've got. Hope that helped!
Listens to K-Pop (Twice, Red Velvet, MAMAMOO) and Christmas music all year round.

Erutepa

  • VIC MVP - 2019
  • Forum Leader
  • ****
  • Posts: 721
  • evenin'
  • Respect: +775
Re: VCE Chemistry Question Thread
« Reply #8179 on: October 16, 2019, 09:49:22 pm »
+3
Hello,
More questions; sorry !!
-Do we need to memorise Faraday's laws?
-Is the cathode positive in the secondary cell??
-Actually could sombody please just give me a super quick summary of secondary cells (probably also fuel cells) and which way the recharges and discharges (i.e.just something super basic like the top equation, oxidation (or is it reduction now???) goes L to R on the electrochem series).
-And Electrolytic cells too, please!

Sorry, I am just so unutterably confused about this topic  :-[  and I've watched a bunch of youtube videos and looked through my summary notes and books but I don't get it yet. I think that I've got the Galvanic cells down but the rest of this is just a tangled mess in my head. We had this random period of time where our chemistry teacher left and our classes were covered by CRTs for a while before we got a new teacher and I guess this is one of those topics that suffered immensely :(

Thank you in advance :)
1) No you don't need to memorise faraday's law - its in the data booklet as:

where Q is the magnitude of charge (product of current and time) and F is faraday's constant (also in the data booklet as 96500)

2) In any electrochemical cell during discharge:
 - Anode=oxidation=negative
 - Cathode=reduction=positive
In any electrochemical cell during recharge
 - Anode=oxidation=positive
 - Cathode=reduction=negative

3) I have to go to bed now, so can't give a summary of it here right now. I did give a brief explanation that might help here: https://atarnotes.com/forum/index.php?topic=188141.msg1137087#new
You might also want to have a look around the notes section of ATAR notes - past chemistry lectures slides have pretty good summaries in them which may help and you might even be able to find summary notes made by others.
Qualifications
 > Have counted to 227
 > Can draw really good spiders
 > 2 Poet points
 > 6.5 insanipi points
 > 1 Bri MT point

EllingtonFeint

  • Trendsetter
  • **
  • Posts: 153
  • Offering private tutoring ✨
  • Respect: +24
Re: VCE Chemistry Question Thread
« Reply #8180 on: October 17, 2019, 06:11:27 pm »
0
Hey,
Does anyone have any tips on how to remember the reaction pathways (like substitution reactions and stuff) as well as all the reactants needed (KMnO7 2- etc. (??))

I'm struggling to fit it all in my brain :/
Biology 🌱 [49] |  English [47]

Surviving and Succeeding in Biology:
https://atarnotes.com/forum/index.php?topic=187145.msg1129188

colline

  • MOTM: NOV 19
  • Forum Obsessive
  • ***
  • Posts: 341
  • ♡ 2 Timothy 1:7 ♡
  • Respect: +512
Re: VCE Chemistry Question Thread
« Reply #8181 on: October 17, 2019, 06:23:09 pm »
+5
Hey,
Does anyone have any tips on how to remember the reaction pathways (like substitution reactions and stuff) as well as all the reactants needed (KMnO7 2- etc. (??))

I'm struggling to fit it all in my brain :/
I drew up a reaction pathways diagram and stuck it to my bathroom wall so I spend a good chunk of my time staring at it until it becomes engrained in my mind.

That, and I guess just grinding through questions until everything eventually becomes muscle memory.

Sorry if that’s crap advice but I don’t link there’s much of a cheat way to this.

VCE: Literature [50] Methods [50] Further [48] Chemistry [40] Biology [33]
2022: Bachelor of Science (Mathematical Economics) @ ANU

EllingtonFeint

  • Trendsetter
  • **
  • Posts: 153
  • Offering private tutoring ✨
  • Respect: +24
Re: VCE Chemistry Question Thread
« Reply #8182 on: October 17, 2019, 08:25:02 pm »
0
Hey,
I'm confused about how to do part C of this question.
The solutions say to use the n=V/Vm... what exactly is Vm and how do I find it??


*Also, another question. Sorry guys!
For the second pic, the one showing the mass spectrum, how am I possibly able to tell what the molecular formula of the parent molecule is? Is there some kinda rule I'm missing? Cos surely, (I mean I know this is so like way off but whatevs) you could have CH47N??


Thanks!  :D
« Last Edit: October 17, 2019, 08:53:42 pm by EllingtonFeint »
Biology 🌱 [49] |  English [47]

Surviving and Succeeding in Biology:
https://atarnotes.com/forum/index.php?topic=187145.msg1129188

sweetiepi

  • National Moderator
  • ATAR Notes Legend
  • *****
  • Posts: 4767
  • "A Bit of Chaos" (she/they)
  • Respect: +3589
Re: VCE Chemistry Question Thread
« Reply #8183 on: October 17, 2019, 09:29:28 pm »
+5
Hey,
I'm confused about how to do part C of this question.
The solutions say to use the n=V/Vm... what exactly is Vm and how do I find it??
Hey!
\(\text{V}_m\) is the volume of a gas at 1 mol, and is known as the molar volume!
This can be calculated by rearranging the ideal gas law- \(\text{PV} = \text{nRT}\), solving for \(\text{V}\). Assuming standard lab conditions- 100 kPa, 298.15K, and that we're calculating the volume for 1 mol, you can substitute in the values and then use this value to use \(\text{n}(\ce{O2})=\frac{\text{V}}{\text{V}_m}\) to find the moles of \(\ce{O2}\)!

I hope this helps!!! :)
2017-2019: Bachelor of Pharmaceutical Science (Formulation Science)
2020: Bachelor of Pharmaceutical Science (Honours) Read my uni journey here!

Bri MT

  • VIC MVP - 2018
  • Administrator
  • ATAR Notes Legend
  • *****
  • Posts: 4719
  • invest in wellbeing so it can invest in you
  • Respect: +3677
Re: VCE Chemistry Question Thread
« Reply #8184 on: October 17, 2019, 09:48:29 pm »
+4
*Also, another question. Sorry guys!
For the second pic, the one showing the mass spectrum, how am I possibly able to tell what the molecular formula of the parent molecule is? Is there some kinda rule I'm missing? Cos surely, (I mean I know this is so like way off but whatevs) you could have CH47N??


Thanks!  :D

Except you know that you couldn't have CH47N as it doesn't make sense for that molecule to exist. Often you would use mass spec in conjunction with other info. Definitely easier if you can get the empirical formula first (e.g. CnH2n+2) and then use mass spec to solve for n

colline

  • MOTM: NOV 19
  • Forum Obsessive
  • ***
  • Posts: 341
  • ♡ 2 Timothy 1:7 ♡
  • Respect: +512
Re: VCE Chemistry Question Thread
« Reply #8185 on: October 18, 2019, 10:35:54 am »
0
On the 2017 NHT examiners reports, they’ve expressed the molar heat of combustion (delta H_c) as a negative value. However I thought that
- Molar heat of combustion is always positive
- The enthalpy (delta H) can be either positive or negative

Is my understanding correct and did VCAA make a mistake, or is there something that I am not aware of?

See Q10c (top of page 11) of https://www.vcaa.vic.edu.au/Documents/exams/chemistry/2017/nht/chemistrynht_examrep17.pdf

Thanks.

VCE: Literature [50] Methods [50] Further [48] Chemistry [40] Biology [33]
2022: Bachelor of Science (Mathematical Economics) @ ANU

hums_student

  • MOTM: SEP 18
  • Forum Obsessive
  • ***
  • Posts: 379
  • Respect: +520
Re: VCE Chemistry Question Thread
« Reply #8186 on: October 18, 2019, 10:46:40 am »
+2
On the 2017 NHT examiners reports, they’ve expressed the molar heat of combustion (delta H_c) as a negative value. However I thought that
- Molar heat of combustion is always positive
- The enthalpy (delta H) can be either positive or negative

Is my understanding correct and did VCAA make a mistake, or is there something that I am not aware of?

Your understanding is correct, it is a mistake on VCAA's part. Delta Hc is always a positive value.
2019-21: Bachelor of Arts (Politics & Int'l Relations / Economics)

EllingtonFeint

  • Trendsetter
  • **
  • Posts: 153
  • Offering private tutoring ✨
  • Respect: +24
Re: VCE Chemistry Question Thread
« Reply #8187 on: October 18, 2019, 11:11:32 am »
0
Hey,
-So on the 2018 exam there's a 3 mark q about vitamin C being a coenzyme.
I understand the first two marks being about the function of a coenzyme and the active site and stuff but the third mark says...

In this synthesis ascorbic acid is oxidised during oxidation and reformed during reduction steps; hence, acting as an electron carrier/acts as a reductant by donating electrons to the enzyme substrate complex to facilitate reaction.

This wasn't in my textbook. Is this something we're just expected to know?? Do ALL coenzymes behave like this?? I don't even really understand what half of it means :(


-Also could somebody please give me a concise short definition of geometric isomers please :)


Thank youuu :)

Biology 🌱 [49] |  English [47]

Surviving and Succeeding in Biology:
https://atarnotes.com/forum/index.php?topic=187145.msg1129188

colline

  • MOTM: NOV 19
  • Forum Obsessive
  • ***
  • Posts: 341
  • ♡ 2 Timothy 1:7 ♡
  • Respect: +512
Re: VCE Chemistry Question Thread
« Reply #8188 on: October 18, 2019, 02:17:07 pm »
+4
Your understanding is correct, it is a mistake on VCAA's part. Delta Hc is always a positive value.
Thanks!

Also could somebody please give me a concise short definition of geometric isomers please :)
- Only occurs if there is a DOUBLE bond between the carbons
- Does NOT apply when one or more of the carbons have 2 identical substituents (ie if 2 of the same atoms are on one side of the double bond)
- Distinction between 'cis' and 'trans' -- 'cis' means that the two are on the same side, 'trans' means they're on different sides. (see image)




Hope that clears it up a little! I'm not too sure about your other questions but hopefully someone else can help ^-^

VCE: Literature [50] Methods [50] Further [48] Chemistry [40] Biology [33]
2022: Bachelor of Science (Mathematical Economics) @ ANU

alanihale

  • Forum Regular
  • **
  • Posts: 53
  • i still haven't taken my L's yet :(
  • Respect: +31
Re: VCE Chemistry Question Thread
« Reply #8189 on: October 18, 2019, 06:52:09 pm »
0
Your understanding is correct, it is a mistake on VCAA's part. Delta Hc is always a positive value.
I thought it was that delta Hc always had to be negative as the heat energy is being released. Is that not it?
2018 - Further Maths [44]
2019 - English [45] | Spesh [hahaha] | Methods [40] | Chem [41] | Bio [40]
Atar: 98.55

Bachelor of Dental Science (Honours) @ La Trobe

---
'Hard work beats talent when talent fails to work hard'