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AQA CHEM4 - 13th June 2012

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    (Original post by masterhr1)
    When an chiral compound is formed at the end of a reaction, how can we tell if it's a racemic mixture that's formed?


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    It's always formed as a racemic mixture. Because the species attacking the compound has equal probability of attack from above and below the plane - leading to equal amounts of each enantimer/racemate
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    Topics I'm really scared for is as follows:

    rate equations
    equilibrium constant
    acids, bases and pH calculations
    pH curves, titration and indicators
    titration calculation
    BUFFER BSSSSS



    can someone post every related question to this topic onto here from 2002 and we'll completely dominate these types of questions.
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    (Original post by Casshern1456)
    Topics I'm really scared for is as follows:

    rate equations
    equilibrium constant
    acids, bases and pH calculations
    pH curves, titration and indicators
    titration calculation
    BUFFER BSSSSS



    can someone post every related question to this topic onto here from 2002 and we'll completely dominate these types of questions.
    How are you finding NMR?

    What are you finding hard in the topics you said? I'll try help
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    (Original post by Doctor.)
    I agree with the "-N-Trimethyl" its the bit before that, I disagree with though.

    Where are you getting the Propanoic acid from? That part could have been been an Aldehyde?

    I would say its Propanamide N-trimthyl

    Nice that covers the CH3CH2CON bit and ofcoure the N-(CH3)3 bit is correct?

    That's just what I think though
    you're correct, my bad. I would write it N-methyl propanamide though. Propanamide because its essentially an aldehyde with a amine group attached. got it.
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    (Original post by callmenighthawk)
    you're correct, my bad. I would write it N-methyl propanamide though. Propanamide because its essentially an aldehyde with a amine group attached. got it.
    Yeah I see what you mean, I hate naming it when they hace the N- makes everything complicated :sigh:
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    (Original post by Doctor.)
    Yeah I see what you mean, I hate naming it when they hace the N- makes everything complicated :sigh:
    I think of the N as like a number - like 1-methyl etc, I'm not sure if it works.
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    (Original post by MuffinMonster)
    I think of the N as like a number - like 1-methyl etc, I'm not sure if it works.
    Kinda, except the N just basically says what is on the N, rather than saying where it is (because obviously there is only one N in the molecule)
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    Can someone explain on how to do the proton nmr stuff like working out integration values and integration ratios???
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    (Original post by shuaib786)
    Can someone explain on how to do the proton nmr stuff like working out integration values and integration ratios???
    You'll be given the integration values in the exam so don't worry about that. To get the ratios, just get the lowest common multiple between the numbers and you're done.
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    (Original post by Doctor.)
    You'll be given the integration values in the exam so don't worry about that. To get the ratios, just get the lowest common multiple between the numbers and you're done.
    So thanks how would you do the 8 c) i) and ii) from the chem 4 jan 2006 paper from the old spec.
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    Unit 5..... So much memorising compare to unit 4 !! Any better ways to revise unit 5 ???


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    (Original post by shuaib786)
    So thanks how would you do the 8 c) i) and ii) from the chem 4 jan 2006 paper from the old spec.
    I'll have a look at it tomorrkw, but be a little wary the old spec did have emphasis on certain topics and less emphasis on others.
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    (Original post by xiyangliu)
    Unit 5..... So much memorising compare to unit 4 !! Any better ways to revise unit 5 ???


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    Unit 5 isn't much memorising tbh. It's all about understanding what it going on. So make sure you get exactly what is happening, then question yourself..."but why is it doing that?" - it helps!!!
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    (Original post by Doctor.)
    I'll have a look at it tomorrkw, but be a little wary the old spec did have emphasis on certain topics and less emphasis on others.
    yh plz
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    (Original post by shuaib786)
    yh plz
    Sorry didnt manage to take a look today. Had a ton of other revision to do. Will try take a look tomorrow again sorry!
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    Click image for larger version. 

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    anyone know the answer to the number of peaks
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    ANYONE HAVE THE JAN 2012 UNIT 4 CHEM PAPER ??!!

    pleaseeeeeeeee
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    (Original post by rss.914)
    Click image for larger version. 

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    anyone know the answer to the number of peaks
    five I think
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    (Original post by Mero8)
    five I think
    how did you get 5? thats the right answer. ii could only get 4
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    (Original post by rss.914)
    how did you get 5? thats the right answer. ii could only get 4
    because you get 5 groups starting from the most electronegative substance the oxygen, so when you count the protons at every different occurring position along the chain the Hydrogen it is in will affect how many peaks there are. The 2 CH3 group on the second Carbon count as 1 for example.

    Click image for larger version. 

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