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Edexcel - Chemistry Unit 2 - 4 June 2013 Watch

  • View Poll Results: Which topic(s) are you finding most difficult?
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    (Original post by Priya08)
    maybe this helps:Attachment 221140
    Therefore A is an elimination reaction and D is a nucleiophillic sub reaction
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    (Original post by Priya08)
    Therefore A is an elimination reaction and D is a nucleiophillic sub reaction
    Yeah but for reaction B theres 2 possible mechanisims depending on whether its a primary or tertiary halogenoalkane C4H9br.. Kinda confused why are there 2 and why does the structuce effect the mechanism?
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    (Original post by scientific222)
    Its been slowly creeping up, it was 63/80 in June 2012 and now 65/80 for Jan 2013's paper (which was real hard in my opinion). That is really insane considering its a paper where mistakes can be made so easily
    I too am terrified about grade boundaries.
    I hope this paper is very hard so the grade boundaries drop.
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    Going to open a forum for any questions on this so I can answer them all, look out for it.
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    (Original post by Kenzo-k)
    Yeah but for reaction B theres 2 possible mechanisims depending on whether its a primary or tertiary halogenoalkane C4H9br.. Kinda confused why are there 2 and why does the structuce effect the mechanism?
    If tertiary the c-br bond breaks, so a carbocation is formed and the OH- nucleiophile attacks the carbocation to form the alcohol

    If its primary the OH- nucliophile adds to the halogen alkane first and then the c-br bond breaks

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    What state is PI3?
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    (Original post by posthumus)
    Alkane + Halogen (with UV rays) ----> Halogenoalkane

    Halogenoalkane + NaOH -----> Alcohol + NaX

    Alcohol + potassium dichromate -----> Carboxylic acid + H2O

    [conditions being: dilute H2SO4... heat under reflux]

    ?????
    Yah, nice one.
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    (Original post by Jayqwe)
    What state is PI3?
    Aqueous because it is made in moist conditions inorder to produce iodoalkane

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    (Original post by HarryMWilliams)
    The 3 alkyl groups feed their electrons to the carbocation, hence, it forms a much more stable intermediate that primary and secondary alcohols, it's therefore more 'available' to react - the fact theres 3 alkyl groups also means the halogen group can leave easier. That's my understanding at least.



    Very good.

    But! You're missing a hydrogen in your haloalkane.
    :confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused: why you no type 3 why u type 2 only loser type 2... :cool::rolleyes::eek::eek::cool::rolleyes::rolleyes::confused::confused:
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    (Original post by HarryMWilliams)
    I was a bit mean but not that bad, that said, I also hope the June paper is nicer.

    **January 2013 paper here!**
    tnx so much, do you have the answers ?
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    (Original post by HarryMWilliams)
    Yah, nice one.
    Just realized someone got it before me, damn it !

    I was a bit unsure about the second step... because it's not a tertiary alcohol. But I guess it goes under Sn2 mechanism instead anyway
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    (Original post by Goods)
    :confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused::confused: why you no type 3 why u type 2 only loser type 2... :cool::rolleyes::eek::eek::cool::rolleyes::rolleyes::confused::confused:
    Sorry, what?

    (Original post by Baraf)
    tnx so much, do you have the answers ?
    MS is here: http://www.thestudentroom.co.uk/atta...ntid=203014‎

    (Original post by posthumus)
    Just realized someone got it before me, damn it !

    I was a bit unsure about the second step... because it's not a tertiary alcohol. But I guess it goes under Sn2 mechanism instead anyway
    It's all the same final product, effectively anyway.
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    anyone is clear on what exactly an activated complex is? how does its formation mean a lower activation energy?
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    (Original post by Kurraiyo)
    anyone is clear on what exactly an activated complex is? how does its formation mean a lower activation energy?
    Its a transition stage that a reaction can occur by, like half breaking the bonds forming the activated complex then breaking the other half for completion. And so it requires less energy than a one stage mechanism
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    (Original post by Goods)
    Its a transition stage that a reaction can occur by, like half breaking the bonds forming the activated complex then breaking the other half for completion. And so it requires less energy than a one stage mechanism
    Is this in the sylabbus?

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    http://www.edexcel.com/migrationdocu...e_20090603.pdf I don't understand q10 b as I thought it will shift to the right and so increase yield? Thanks
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    (Original post by Priya08)
    Is this in the sylabbus?

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    Theres a paragraph about them in reference to SN2 mechanisms in a chemistry book I have. I don't think we would get a question about it
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    (Original post by SophieL1996)
    http://www.edexcel.com/migrationdocu...e_20090603.pdf I don't understand q10 b as I thought it will shift to the right and so increase yield? Thanks
    3 moles ----> 5 moles

    Decreasing the pressure causes EQM to oppose this change and side with the greater moles therefore moves forward

    So yield increases but rate decreases as pressure is decreasing and less collision occurs between particles

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    (Original post by SophieL1996)
    http://www.edexcel.com/migrationdocu...e_20090603.pdf I don't understand q10 b as I thought it will shift to the right and so increase yield? Thanks
    decrease in pressure, therefore the equilibrium point shifts to the left to produce more moles of gas.
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    (Original post by Priya08)
    3 moles ----> 5 moles
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    only consider moles of gas.
 
 
 
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