Login

Welcome, Guest. Please login or register.

March 28, 2024, 11:12:28 pm

Author Topic: VCE Chemistry Question Thread  (Read 2313097 times)  Share 

0 Members and 10 Guests are viewing this topic.

swagsxcboi

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 367
  • Respect: +4
  • School Grad Year: 2014
Re: VCE Chemistry Question Thread
« Reply #540 on: March 29, 2014, 09:50:00 pm »
0
how many decimal places do we express Rf values to?
2013: Biology [47]

2014 AIMS: English (37)    Methods (37)    Business Management (30)    Chemistry (40)


2015 AIMS:
Applied Science/Physiotherapy Practice at La Trobe

Feel free to PM me about Bio or anything :)

Yacoubb

  • Guest
Re: VCE Chemistry Question Thread
« Reply #541 on: March 30, 2014, 01:12:48 am »
0
how many decimal places do we express Rf values to?

Usually 2.

swagsxcboi

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 367
  • Respect: +4
  • School Grad Year: 2014
Re: VCE Chemistry Question Thread
« Reply #542 on: March 30, 2014, 11:18:20 am »
0
Usually 2.
so if get 8.777
then i'd express it as 8.78?
2013: Biology [47]

2014 AIMS: English (37)    Methods (37)    Business Management (30)    Chemistry (40)


2015 AIMS:
Applied Science/Physiotherapy Practice at La Trobe

Feel free to PM me about Bio or anything :)

Yacoubb

  • Guest
Re: VCE Chemistry Question Thread
« Reply #543 on: March 30, 2014, 11:35:38 am »
+2
so if get 8.777
then i'd express it as 8.78?

Rf values are always below or equal to 1. But yes, if you got 0.777, that would be 0.78

swagsxcboi

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 367
  • Respect: +4
  • School Grad Year: 2014
Re: VCE Chemistry Question Thread
« Reply #544 on: March 30, 2014, 03:47:11 pm »
0
Rf values are always below or equal to 1. But yes, if you got 0.777, that would be 0.78
LOL my bad wow hahahaha
thank you Yacoubb!!
2013: Biology [47]

2014 AIMS: English (37)    Methods (37)    Business Management (30)    Chemistry (40)


2015 AIMS:
Applied Science/Physiotherapy Practice at La Trobe

Feel free to PM me about Bio or anything :)

maurlock

  • Victorian
  • Adventurer
  • *
  • Posts: 20
  • Respect: 0
Re: VCE Chemistry Question Thread
« Reply #545 on: April 05, 2014, 09:41:15 pm »
0
why will the ratio of n(base):n(acid) for a dicarboxylic acid reacting with NaOH be 2:1?

jgoudie

  • Victorian
  • Trendsetter
  • **
  • Posts: 138
  • Chemisode: an app for studying chemistry
  • Respect: +3
Re: VCE Chemistry Question Thread
« Reply #546 on: April 05, 2014, 10:03:34 pm »
+3
Acid:Base ratio is really a ratio of H+:OH-, A dicarboxylic acid has two COOH's that lose their hydrogens, sodium hydroxide only has one OH, so twice as much n(NaOH) is required.

thus the H+ : OH- is 1:2

why will the ratio of n(base):n(acid) for a dicarboxylic acid reacting with NaOH be 2:1?
Chemisode: A podcast, iPhone/iPad app for studying VCE chemistry.

Search the appstore: "Chemisode"
http://www.facebook/chemisode34
http://www.facebook/chemisode12
http://jgoudie.podomatic.com/
http://www.youtube.com/mrjasongoudie
Iphone and Ipad apps: 'Chemisode' out in the app store now!

maurlock

  • Victorian
  • Adventurer
  • *
  • Posts: 20
  • Respect: 0
Re: VCE Chemistry Question Thread
« Reply #547 on: April 05, 2014, 10:05:46 pm »
0
Thank you so much!

Rishi97

  • Victorian
  • Part of the furniture
  • *****
  • Posts: 1042
  • Respect: +40
  • School: The University of Melbourne
  • School Grad Year: 2014
Re: VCE Chemistry Question Thread
« Reply #548 on: April 07, 2014, 08:45:11 pm »
0
Can someone pls explain figure 12.13b from pg 185 of the heinemann textbook?
In the glycosidic linkage, where did the HOCH2 come from? I understand that there is a water molecule being released so that should just leave CH2 bonding with H shouldn't it? And oxygen for the glycosidic bond.
Hope you can make some sense of what I wrote here :P
2014: VCE completed
2015-2017: BSc at Melb Uni

DREAM, BELIEVE, ACHIEVE!!!

nhmn0301

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 379
  • Respect: +15
  • School: The University of Melboure
  • School Grad Year: 2017
Re: VCE Chemistry Question Thread
« Reply #549 on: April 08, 2014, 11:13:48 am »
0
Can someone pls explain figure 12.13b from pg 185 of the heinemann textbook?
In the glycosidic linkage, where did the HOCH2 come from? I understand that there is a water molecule being released so that should just leave CH2 bonding with H shouldn't it? And oxygen for the glycosidic bond.
Hope you can make some sense of what I wrote here :P
I think the textbook got some mistakes with that fructose structure, as far as Im aware, isn't the OH supposed to be branching from the same carbon with an CH2OH ? thats why there an CH2OH in the next photo.
I think I figure out the problem here, there is a mistake in textbook, according to my 2010 version textbook, it looks exactly like your photo, however, according to another version of the textbook, it's CH2OH.
Hope this helps!
« Last Edit: April 08, 2014, 11:19:35 am by nhmn0301 »
2015-2017: Bachelor of Biomedicine

Rishi97

  • Victorian
  • Part of the furniture
  • *****
  • Posts: 1042
  • Respect: +40
  • School: The University of Melbourne
  • School Grad Year: 2014
Re: VCE Chemistry Question Thread
« Reply #550 on: April 08, 2014, 11:21:46 am »
+1
I think the textbook got some mistakes with that fructose structure, as far as Im aware, isn't the OH supposed to be branching from the same carbon with an CH2OH ? thats why there an CH2OH in the next photo.
I think I figure out the problem here, there is a mistake in textbook, according to my 2010 version textbook, it looks exactly like your photo, however, according to another version of the textbook, it's CH2OH.
Hope this helps!

If that is the case, then the diagram makes sense. I think the diagram is wrong cause the CH2OH should be on the same branch as OH. Yeah, I'm pretty sure your're right. Thanks :D
Could someone pls confirm our theory
2014: VCE completed
2015-2017: BSc at Melb Uni

DREAM, BELIEVE, ACHIEVE!!!

scribble

  • is sexier than Cthulhu
  • Victorian
  • Forum Leader
  • ****
  • Posts: 814
  • Respect: +145
  • School Grad Year: 2012
Re: VCE Chemistry Question Thread
« Reply #551 on: April 08, 2014, 11:34:12 am »
0
i remember the diagram being wrong in my edition of the textbook. i wouldn't be surprised if they didnt correct it in the current edition.

Blondie21

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 489
  • Respect: +13
  • School: Lakeview Senior College
  • School Grad Year: 2014
Re: VCE Chemistry Question Thread
« Reply #552 on: April 08, 2014, 05:03:20 pm »
+1
On a mass spectrum of ethanoic acid, is there no peak for OH- because it is an negative ion?
'15 - '17: The University of Melbourne - Bachelor of Science

lzxnl

  • Victorian
  • ATAR Notes Legend
  • *******
  • Posts: 3432
  • Respect: +215
Re: VCE Chemistry Question Thread
« Reply #553 on: April 08, 2014, 05:30:59 pm »
0
I can't imagine how you'd form that negative ion. The electrons in the mass spectrometer are so energetic they can't be captured by molecules and radicals. That's why they knock out other electrons.
2012
Mathematical Methods (50) Chinese SL (45~52)

2013
English Language (50) Chemistry (50) Specialist Mathematics (49~54.9) Physics (49) UMEP Physics (96%) ATAR 99.95

2014-2016: University of Melbourne, Bachelor of Science, Diploma in Mathematical Sciences (Applied Maths)

2017-2018: Master of Science (Applied Mathematics)

2019-2024: PhD, MIT (Applied Mathematics)

Accepting students for VCE tutoring in Maths Methods, Specialist Maths and Physics! (and university maths/physics too) PM for more details

Blondie21

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 489
  • Respect: +13
  • School: Lakeview Senior College
  • School Grad Year: 2014
Re: VCE Chemistry Question Thread
« Reply #554 on: April 08, 2014, 05:42:16 pm »
+1
I can't imagine how you'd form that negative ion. The electrons in the mass spectrometer are so energetic they can't be captured by molecules and radicals. That's why they knock out other electrons.

I'm a little confused

During the fragmentation process, there is a loss of CH3+ to form a COOH+ from ethanoic acid and both of these are on the mass spectrum

However, when there is a loss of OH (forming CH3CO+ then CH2CO+), the OH is not in the mass spectrum. Why?
'15 - '17: The University of Melbourne - Bachelor of Science