Anyone want help with AS AQA Chemistry? Watch

t.thompson22
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I can only do AQA and I haven't be taught redox yet so I can't do that. However, post any questions you have whether their from homeworks, past papers etc!
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derpz
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Post some questions in this thread, I'll be posting some that I dont understand or am stuck on later
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t.thompson22
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(Original post by derpz)
Post some questions in this thread, I'll be posting some that I dont understand or am stuck on later
I've been working through past papers all week, I can post some organic chemistry questions tomorrow? Mainly mechanisms.
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derpz
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(Original post by t.thompson22)
I've been working through past papers all week, I can post some organic chemistry questions tomorrow? Mainly mechanisms.
I've not completed all of the organic content yet but sure, any revision is helpful


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derpz
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Could someone outline the key differences between the 3 types of isomers:
- chain isomers
- position isomers
- functional group isomers

I dont understand how you differentiate between them and how to draw each of them for an organic compound e.g. what part do you cahnge for each?
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t.thompson22
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(Original post by derpz)
Could someone outline the key differences between the 3 types of isomers:
- chain isomers
- position isomers
- functional group isomers

I dont understand how you differentiate between them and how to draw each of them for an organic compound e.g. what part do you cahnge for each?
Chain isomerism is when the main carbon chain is arranged differently. For example, take straight-chained butane. A chain isomer of butane could be 2-methylpropane. In this case, it's a branched molecule instead of being straight-chained.

Positional isomerism refers to the functional group being in a different POSITION in the molecule. Take but-2-ene with the carbon-carbon double bond on the second carbon atom. A positional isomer could be but-1-ene with the double bond on the first carbon atom instead. Or in pentan-2-ol, a positional isomer would be pentan-3-ol.

Functional group isomerism is when the molecule has a different functional group, do you know your functional groups? In an alcohol it's the hydroxyl group. In an alkene it's the carbon-carbon double bond. A functional group isomer of an alkene could be a cycloalkane as you've gotten rid of the double bond.

I don't mind drawing any of these out if you wish!
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derpz
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(Original post by t.thompson22)
Chain isomerism is when the main carbon chain is arranged differently. For example, take straight-chained butane. A chain isomer of butane could be 2-methylpropane. In this case, it's a branched molecule instead of being straight-chained.

Positional isomerism refers to the functional group being in a different POSITION in the molecule. Take but-2-ene with the carbon-carbon double bond on the second carbon atom. A positional isomer could be but-1-ene with the double bond on the first carbon atom instead. Or in pentan-2-ol, a positional isomer would be pentan-3-ol.

Functional group isomerism is when the molecule has a different functional group, do you know your functional groups? In an alcohol it's the hydroxyl group. In an alkene it's the carbon-carbon double bond. A functional group isomer of an alkene could be a cycloalkane as you've gotten rid of the double bond.

I don't mind drawing any of these out if you wish!
So would these summaries be correct? :

Chain isomer - change the length of the longest carbon chain

Position isomer - change only the position of the functional group, so bascialy which carbon it is connected to

Functoinal group - rearrange it to form a different functional group e.g. an alkane into an alkene

Are these summaries correct?
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t.thompson22
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(Original post by derpz)
So would these summaries be correct? :

Chain isomer - change the length of the longest carbon chain

Position isomer - change only the position of the functional group, so bascialy which carbon it is connected to

Functoinal group - rearrange it to form a different functional group e.g. an alkane into an alkene

Are these summaries correct?
Yeah these are good! That's a great way to remember it.
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Squishy•
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(Original post by derpz)
So would these summaries be correct? :

Chain isomer - change the length of the longest carbon chain

Position isomer - change only the position of the functional group, so bascialy which carbon it is connected to

Functoinal group - rearrange it to form a different functional group e.g. an alkane into an alkene

Are these summaries correct?
Remember that the whole point of isomerism is that they all have the same molecular formular.
You can't do Alkane into an Alkene just like that as the number of hydrogen a wont match up as two of the carbons have one less bond available for Hydrogen. You can however do a cycloalkane to Alkene .
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Squishy•
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I got an A in AQA Chem AS last year guys so quote me if u need help.
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derpz
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(Original post by Squishy•)
Remember that the whole point of isomerism is that they all have the same molecular formular.
You can't do Alkane into an Alkene just like that as the number of hydrogen a wont match up as two of the carbons have one less bond available for Hydrogen. You can however do a cycloalkane to Alkene .
Yeah, good point. SO change it as long as the structural forumla is the exact same
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t.thompson22
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(Original post by Squishy•)
I got an A in AQA Chem AS last year guys so quote me if u need help.
What's the optimal amount of past papers I should do before the exam & do you have any tips on exam technique? Like how to remember the specific language that the examiners are for?
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Squishy•
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(Original post by derpz)
Yeah, good point. SO change it as long as the structural forumla is the exact same
Molecular formula.
As they have different structures
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Squishy•
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(Original post by t.thompson22)
What's the optimal amount of past papers I should do before the exam & do you have any tips on exam technique? Like how to remember the specific language that the examiners are for?
Do them all and do all the questions in the books. When you do them and get used to marking them, the trends in mark schemes stick in your mind and you know how the language to use and what the question is asking for.
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derpz
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(Original post by Squishy•)
Molecular formula.
As they have different structures
Im getting confused, the displayed is drawn out, and what about the structural then? I know the skeletal uses the backbone etc
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t.thompson22
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(Original post by derpz)
Im getting confused, the displayed is drawn out, and what about the structural then? I know the skeletal uses the backbone etc
Displayed in when you draw all atoms and bonds, with structural, let's take Propane. It's structural formulae would be CH3CH2CH3 only.
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Squishy•
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(Original post by derpz)
Im getting confused, the displayed is drawn out, and what about the structural then? I know the skeletal uses the backbone etc
Molecular formular of Ethene would be C2H4
Whereas the structural formular is CH2CH2, sometime drawn as H2C=CH2, the structural shows the arrangement of atoms, the displayed shows all the bonds in the molecule and the skeletal shows just the carbon bonds and any other external atoms(other than C and H).
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derpz
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(Original post by t.thompson22)
Displayed in when you draw all atoms and bonds, with structural, let's take Propane. It's structural formulae would be CH3CH2CH3 only.
Oh right that makes more sense, so the structural sort of shows it in chronological order whereas the molecular shows how many carbons and hydrogens in one
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t.thompson22
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(Original post by derpz)
Oh right that makes more sense, so the structural sort of shows it in chronological order whereas the molecular shows how many carbons and hydrogens in one
Yes you could say that. Molecular formulae of propane is C3H8. Structural formulae would be CH3CH2CH3. See the difference? To check if your structural formalae is correct, just count the number of separate atoms and ensure it corresponds to other formula given
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derpz
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(Original post by t.thompson22)
Yes you could say that. Molecular formulae of propane is C3H8. Structural formulae would be CH3CH2CH3. See the difference?
Yep, got it now. Thanks!

My teacher is terrible, so I'm mostly just having to self teach myself so sorry about all these questions, I'll be asking a lot of stuff hahaha
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