Login

Welcome, Guest. Please login or register.

March 28, 2024, 07:11:39 pm

Author Topic: VCE Chemistry Question Thread  (Read 2312952 times)  Share 

0 Members and 1 Guest are viewing this topic.

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 #765 on: April 27, 2014, 12:26:19 pm »
0
ok so how would an ethyl group be represented

if (CH2)2 means just 2 CH2 chains would ethyl be (CH2CH3)?

Yes an ethyl group is CH2CH3
2014: VCE completed
2015-2017: BSc at Melb Uni

DREAM, BELIEVE, ACHIEVE!!!

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 #766 on: April 27, 2014, 12:28:50 pm »
0
Could someone please give me a list of what catalysts to use in each reaction? I'm getting really confused what catalysts are meant to be used where
eg. H2SO4 is used during esterification

Greatly appreciated :)
2014: VCE completed
2015-2017: BSc at Melb Uni

DREAM, BELIEVE, ACHIEVE!!!

katiesaliba

  • Victorian
  • Forum Leader
  • ****
  • Posts: 628
  • Respect: +6
  • School: The University of Melbourne
  • School Grad Year: 2017
Re: VCE Chemistry Question Thread
« Reply #767 on: April 27, 2014, 12:32:26 pm »
0
Atomic absorption spectroscopy (AAS) and UV–visible spectroscopy both involve absorption of light. Both can be used to determine the amount of copper in a solution.

b   Which technique would be simplest for the analysis of 0.5 M copper nitrate solution? Explain your answer.

What would be the answer to be and why, because don't both techniques require dilutions? Also, could questions of this calibre be on the exam?
Bachelor of Science (Immunology major) - The University of Melbourne

Yacoubb

  • Guest
Re: VCE Chemistry Question Thread
« Reply #768 on: April 27, 2014, 12:34:35 pm »
+2
Could someone please give me a list of what catalysts to use in each reaction? I'm getting really confused what catalysts are meant to be used where
eg. H2SO4 is used during esterification

Greatly appreciated :)

• UV-light is required in converting alkanes to chloroalkanes.
• Converting alkenes to alcohols requires phosphoric acid + 300oC heat.
• Oxidation of primary alcohols to carboxylic acids requires acidified dichromate, or acidified permanganate.
• Esterification requires concentrated sulfuric acid.
• Chloroalkane --> Alcohol requires NaOH or KOH but that's a reagent!
• Ammonia is needed to produce an amine from a chloroalkane.
• Alkene to alkane (hydrogenation) requires a nickel catalyst + 200oC temperature.

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 #769 on: April 27, 2014, 12:36:08 pm »
0
• UV-light is required in converting alkanes to chloroalkanes.
• Converting alkenes to alcohols requires phosphoric acid + 300oC heat.
• Oxidation of primary alcohols to carboxylic acids requires acidified dichromate, or acidified permanganate.
• Esterification requires concentrated sulfuric acid.
• Chloroalkane --> Alcohol requires NaOH or KOH but that's a reagent!
• Ammonia is needed to produce an amine from a chloroalkane.
• Alkene to alkane (hydrogenation) requires a nickel catalyst + 200oC temperature.

Perfect!!! Just what I wanted. Thanks Yacoubb :)
2014: VCE completed
2015-2017: BSc at Melb Uni

DREAM, BELIEVE, ACHIEVE!!!

Yacoubb

  • Guest
Re: VCE Chemistry Question Thread
« Reply #770 on: April 27, 2014, 12:38:06 pm »
0
Atomic absorption spectroscopy (AAS) and UV–visible spectroscopy both involve absorption of light. Both can be used to determine the amount of copper in a solution.

b   Which technique would be simplest for the analysis of 0.5 M copper nitrate solution? Explain your answer.

What would be the answer to be and why, because don't both techniques require dilutions? Also, could questions of this calibre be on the exam?

I'll have a go, but I could be wrong.
I'd say not AAS. AAS is only reliable for very small concentrations, where the relationship between absorbance and concentration is linear at low concentrations (e.g. Units like ppm). In UV-visible spectroscopy, a coloured solution is required. Cu(NO3)2 is a blue solution, and so this is what makes UV-visible spectroscopy the better option.

darklight

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 213
  • Respect: +2
  • School Grad Year: 2014
Re: VCE Chemistry Question Thread
« Reply #771 on: April 27, 2014, 01:15:44 pm »
0
I'll have a go, but I could be wrong.
I'd say not AAS. AAS is only reliable for very small concentrations, where the relationship between absorbance and concentration is linear at low concentrations (e.g. Units like ppm). In UV-visible spectroscopy, a coloured solution is required. Cu(NO3)2 is a blue solution, and so this is what makes UV-visible spectroscopy the better option.

I thought that colorimetry required coloured solutions, but you can use UV-visible for colourless solutions as well as this technique will utilise UV radiation..
2015: Monash MBBS

swagsxcboi

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 367
  • Respect: +4
  • School Grad Year: 2014
Re: VCE Chemistry Question Thread
« Reply #772 on: April 27, 2014, 01:28:23 pm »
0
I thought that colorimetry required coloured solutions, but you can use UV-visible for colourless solutions as well as this technique will utilise UV radiation..
yeah that's right.



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 #773 on: April 27, 2014, 01:33:50 pm »
0
yeah that's right.




I thought that colorimetry required coloured solutions, but you can use UV-visible for colourless solutions as well as this technique will utilise UV radiation..

Oh yes my bad! What do you guys think though - AAS or UV-Vis?

swagsxcboi

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 367
  • Respect: +4
  • School Grad Year: 2014
Re: VCE Chemistry Question Thread
« Reply #774 on: April 27, 2014, 01:38:56 pm »
0
Oh yes my bad! What do you guys think though - AAS or UV-Vis?
I reckon AAS, it's simpler than UV-Vis and it would get the job done.
just not sure how to answer the question  :P
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 :)

katiesaliba

  • Victorian
  • Forum Leader
  • ****
  • Posts: 628
  • Respect: +6
  • School: The University of Melbourne
  • School Grad Year: 2017
Re: VCE Chemistry Question Thread
« Reply #775 on: April 27, 2014, 01:43:33 pm »
0
So, AAS requires smaller concentrations than UV-Vis for accuracy?
Thanks everyone! :)
Bachelor of Science (Immunology major) - The University of Melbourne

Reus

  • Victorian
  • ATAR Notes Superstar
  • ******
  • Posts: 2125
  • Respect: +135
Re: VCE Chemistry Question Thread
« Reply #776 on: April 27, 2014, 02:23:42 pm »
0
So, AAS requires smaller concentrations than UV-Vis for accuracy?
Thanks everyone! :)

Yes it's AAS.
Btw guys thanks for the answer, however I noticed your questions are like the next few chapter or so, you guys individually ahead or school pace?
2015: Bachelor of Science & Bachelor of Global Studies @ Monash University

soNasty

  • Victorian
  • Forum Leader
  • ****
  • Posts: 531
  • Respect: +11
  • School Grad Year: 2014
Re: VCE Chemistry Question Thread
« Reply #777 on: April 27, 2014, 03:06:54 pm »
0
the answer's UV Vis

Yacoubb

  • Guest
Re: VCE Chemistry Question Thread
« Reply #778 on: April 27, 2014, 03:22:34 pm »
0
the answer's UV Vis

Yeah that's what I said. In Atomic Absorption Spectroscopy, you must dilute that copper nitrate solution to a very low concentration because only at very low concentrations is AAS actually a reliable instrumental technique. In UV-Visible Spectroscopy, those dilutions are not required.

So, the word 'simplest' refers to quickest/most efficient, and in this case, not having to make so many dilutions renders UV-Visible Spec the answer.

Reus

  • Victorian
  • ATAR Notes Superstar
  • ******
  • Posts: 2125
  • Respect: +135
Re: VCE Chemistry Question Thread
« Reply #779 on: April 27, 2014, 03:28:17 pm »
0
Anyone know anything about the Chemistry GTAC SAC? My school has it scheduled in 2 weeks or so, however we haven't discussed it, I'm guessing it's on spectroscopy. You guys done it yet? Any ideas?
2015: Bachelor of Science & Bachelor of Global Studies @ Monash University