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August 22, 2019, 12:15:16 am

Author Topic: VCE Chemistry Question Thread  (Read 914822 times)  Share 

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antigony

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Re: VCE Chemistry Question Thread
« Reply #8085 on: July 22, 2019, 09:27:33 pm »
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I had a quick skim, looks a-okay to me! :)

Great, thanks so much :)

pugs

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Re: VCE Chemistry Question Thread
« Reply #8086 on: July 22, 2019, 10:32:39 pm »
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hey! just wanted to check my answer:

would i be right in saying that the mass of a polymer is the same as the total mass of the monomers that make it up, as nothing new is added? (or does the breaking of the double bond make a difference?)

thanks very much! :)
2018: lote SL
2019: english, biology, chemistry, methods, further maths

2019 vce journal here

sweetcheeks

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Re: VCE Chemistry Question Thread
« Reply #8087 on: July 23, 2019, 01:24:07 pm »
+5
hey! just wanted to check my answer:

would i be right in saying that the mass of a polymer is the same as the total mass of the monomers that make it up, as nothing new is added? (or does the breaking of the double bond make a difference?)

thanks very much! :)

Depends on the polymer. If you are talking about addition polymerisation, then you can say that. However, it would be incorrect if you are talking about polymers in general, as condensation polymerisation results in the loss of a small molecule (e.g. HCl or H2O) and as a result will have a different mass than the combined monomer masses.

antigony

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Re: VCE Chemistry Question Thread
« Reply #8088 on: July 23, 2019, 09:04:41 pm »
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A couple of reaction pathways questions:

- Is a catalyst (AlCl3) needed when reacting an alkene with HCl to produce a chloroalkane?
- When combining a haloalkane and ammonia, is the ammonia in a concentrated solution with ethanol? If yes, must ammonia also be in a solution with ethanol when turning a primary alcohol into an amine via substitution?

Thanks!
« Last Edit: July 23, 2019, 09:06:31 pm by antigony »

pugs

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Re: VCE Chemistry Question Thread
« Reply #8089 on: July 23, 2019, 09:24:56 pm »
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Depends on the polymer. If you are talking about addition polymerisation, then you can say that. However, it would be incorrect if you are talking about polymers in general, as condensation polymerisation results in the loss of a small molecule (e.g. HCl or H2O) and as a result will have a different mass than the combined monomer masses.
oh i forgot about condensation polymerisation thanks! :)
2018: lote SL
2019: english, biology, chemistry, methods, further maths

2019 vce journal here

redpanda83

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Re: VCE Chemistry Question Thread
« Reply #8090 on: July 24, 2019, 12:17:06 am »
+1
A couple of reaction pathways questions:

- Is a catalyst (AlCl3) needed when reacting an alkene with HCl to produce a chloroalkane?
- When combining a haloalkane and ammonia, is the ammonia in a concentrated solution with ethanol? If yes, must ammonia also be in a solution with ethanol when turning a primary alcohol into an amine via substitution?

Thanks!
I dont think a catalyst is required for halogenation of alkenes.
correct me if i am wrong, you cant directly convert alcohol into amine. And yeah concentrated ammonia in ethanol is used to make amines from haloalkanes. like think about it if ammonia and alcohol reacted why would we put them together in this scenario.

antigony

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Re: VCE Chemistry Question Thread
« Reply #8091 on: July 24, 2019, 06:57:41 pm »
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I dont think a catalyst is required for halogenation of alkenes.
correct me if i am wrong, you cant directly convert alcohol into amine. And yeah concentrated ammonia in ethanol is used to make amines from haloalkanes. like think about it if ammonia and alcohol reacted why would we put them together in this scenario.

Thank you for the confirmation about ethanol! I'm pretty sure you can convert an alcohol into an amine though - my teacher has it written in some notes she gave us, and a couple of people from other schools have also confirmed that reaction exists.

redpanda83

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Re: VCE Chemistry Question Thread
« Reply #8092 on: July 24, 2019, 07:18:43 pm »
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Thank you for the confirmation about ethanol! I'm pretty sure you can convert an alcohol into an amine though - my teacher has it written in some notes she gave us, and a couple of people from other schools have also confirmed that reaction exists.
cool. Yeeeee, just remembered you can do it, but its not employed in labs cause hard to control.
direct alkylation of ammonia
R−CH2OH⟶R−CH2NH2
should an acidic medium be used in this case?

jnlfs2010

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Re: VCE Chemistry Question Thread
« Reply #8093 on: July 27, 2019, 08:05:54 pm »
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Do we need to know about each vitamin and where it is sourced?
Do we need to know about all the carbohydrates and where they are sourced?

Thanks

Rom_Dog

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Re: VCE Chemistry Question Thread
« Reply #8094 on: July 28, 2019, 11:41:14 am »
+4
Do we need to know about each vitamin and where it is sourced?
Do we need to know about all the carbohydrates and where they are sourced?

Thanks

From the VCAA study design on vitamins and carbohydrates:

"Vitamins: inability of humans to synthesise most vitamins (except Vitamin D) making them essential dietary
requirements; comparison of structural features of Vitamin C (illustrative of a water-soluble vitamin) and Vitamin D
(illustrative of a fat-soluble vitamin) that determine their solubility in water or oil."

"Carbohydrates: formation of disaccharides from monosaccharides, and of complex carbohydrates (specifically
starch and cellulose) as condensation polymers of monosaccharides; glycosidic links; storage of excess
glucose in the body as glycogen; comparison of glucose, fructose, sucrose and the artificial sweetener
aspartame with reference to their structures and energy content."

In my opinion the key characteristics you need to know about vitamins is that they are needed by the body in small amounts and thus considered micronutrients. Vitamin D and C are commonly used as examples so it benefits you to be familiar with these. Their structures are provided in the data book so there is no need to memorise them however you should know that the presence of hydroxyl groups contributes to the solubility of vitamin C while Vitamin D is largely non-polar and not water soluble (stored in fat).

With carbs, I think it's good to know that polysaccharides form through condensation reactions (H2O as by product) and that starch, cellulose and glycogen are polymers of glucose. Sometimes you'll be asked to name a glycosidic link too.

It's best to refer to the study design for exam study but stick to what you are taught in class for your SACs because teachers may give you questions that require the application of the concepts taught to you in the classroom. Hope this helps!!  :D

2019 - 2021: Biomed @ Monash!

JR_StudyEd

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Re: VCE Chemistry Question Thread
« Reply #8095 on: July 30, 2019, 04:33:00 pm »
+1
I need help with the VCAA 2014 Chem exam, Q2 from Section B. It looks really intimidating and I don't feel like I know enough about reaction pathways to be able to even start off. An explanation of how the diagram works would also be helpful, as I know VCAA like to throw these kinds of questions into exams (and will very likely do so again this year).
VCE Class of 2019
Subjects: English, Psychology (2018), Maths Methods, Chemistry, Biology, Health and Human Development

redpanda83

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Re: VCE Chemistry Question Thread
« Reply #8096 on: July 30, 2019, 05:40:36 pm »
+1
I need help with the VCAA 2014 Chem exam, Q2 from Section B. It looks really intimidating and I don't feel like I know enough about reaction pathways to be able to even start off. An explanation of how the diagram works would also be helpful, as I know VCAA like to throw these kinds of questions into exams (and will very likely do so again this year).
Ethene -> ethanol -> ethanoic acid                                       
prop-1-ene -> 1-chloropropane -> propan-1-ol                         ethanoic acid + propan-1-ol -> propylethanoate
                                |
                          propan-1-amine
use the attachment

Sine

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Re: VCE Chemistry Question Thread
« Reply #8097 on: July 30, 2019, 08:02:33 pm »
+3
I need help with the VCAA 2014 Chem exam, Q2 from Section B. It looks really intimidating and I don't feel like I know enough about reaction pathways to be able to even start off. An explanation of how the diagram works would also be helpful, as I know VCAA like to throw these kinds of questions into exams (and will very likely do so again this year).
The ester pathway is a very important pathway within the context of VCE. You would definitely want to learn thoroughly to the point of memorisation of the whole pathway - including reactants/products and catalysts requried to convert stuff to an alcohol/carboxylic acid and combine them to get an ester.

JR_StudyEd

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Re: VCE Chemistry Question Thread
« Reply #8098 on: August 03, 2019, 10:49:54 am »
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Two questions:

a) What does it mean by 'systematic name'? Is it the same as saying the IUPAC name?
b) Why does hydrolysis result in the production of a carboxylic acid and an alcohol?
VCE Class of 2019
Subjects: English, Psychology (2018), Maths Methods, Chemistry, Biology, Health and Human Development

Jim_Bob

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Re: VCE Chemistry Question Thread
« Reply #8099 on: August 03, 2019, 10:58:02 am »
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Hey guys,
For my chem poster I am doing electrolysis.
We used different voltages per electrolytic cell to test whether voltage has an impact on the mass deposited on the inert cathode. How would I calculate Faraday's Constant to support this hypothesis if I do not know what the Current (Amps) is
Thanks