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OCR Chemistry A Exam Thread (Breadth - May 27 2016 and Depth - June 10 2016) Watch

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    (Original post by asinghj)
    Oh ok.. I do maths and physics and I hate physics too. Chemistry is my favourite. Biology I hate, but I think I didn't do too bad on the papers
    How did you find OCR Physis. i thought depth was really good
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    (Original post by Jitesh)
    Depends on what they give you
    Cl radical + Cl radical -> Cl2 is one for Cl catalysis

    Could be CF2Cl radical + CF2Cl radical -> C2F4CL2 as well for the example earlier
    Ok so just wanted to confirm if this random example is right

    Initiation :
    CF2Cl2 -> CF2Cl• + Cl•

    Propagation:
    Cl• + O3 -> ClO• + O2
    ClO• + O -> Cl• + O2

    Termination:
    Cl• + Cl• -> Cl2
    CF2Cl• + CF2Cl• -> C2F4Cl2

    Did I miss anything out? Also should there be a 3rd termination?
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    (Original post by maxross)
    How did you find OCR Physis. i thought depth was really good
    Our college did AQA for physics and that was horrible! That's great that you found Physics good
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    (Original post by asinghj)
    Ok so just wanted to confirm if this random example is right

    Initiation :
    CF2Cl2 -> CF2Cl• + Cl•

    Propagation:
    Cl• + O3 -> ClO• + O2
    ClO• + O -> Cl• + O2

    Termination:
    Cl• + Cl• -> Cl2
    CF2Cl• + CF2Cl• -> C2F4Cl2

    Did I miss anything out? Also should there be a 3rd termination?
    ClO• + ClO• -> Cl2O2
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    (Original post by asinghj)
    Our college did AQA for physics and that was horrible! That's great that you found Physics good
    oh yeah i have heard about AQA. did you have to cross out a question or something?? haha
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    (Original post by 4nonymous)
    ClO• + ClO• -> Cl2O2
    I was thinking that but didn't know you could have Cl2O2
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    (Original post by maxross)
    oh yeah i have heard about AQA. did you have to cross out a question or something?? haha
    Haha yeah. The question was about identifying the properties of a particle (strangeness, Barton number and charge) which was a question I could have done had AQA not messed it up!
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    What 3 main topics does everyone think will come up? Just want to do some last minute revision on the most probable topics.
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    (Original post by asinghj)
    Haha yeah. The question was about identifying the properties of a particle (strangeness, Barton number and charge) which was a question I could have done had AQA not messed it up!
    how did they mess it up?? what was wrong with it
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    (Original post by bencoughlin)
    What 3 main topics does everyone think will come up. Just want to do some last minute revision on the most probable topics.
    Reaction mechanisms
    Spectroscopy
    Bonding (intermolecular forces, etc)
    But 3 get 1 free:
    Physical trends
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    (Original post by asinghj)
    I was thinking that but didn't know you could have Cl2O2
    All you have to remember for termination is that you just put two radicals together.
    Although could you also do:
    CF2Cl• + Cl• -> CF2Cl2?
    Maybe some others?
    Although they don't tend to ask you for all the termination steps, usually just one or two so should be fine
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    (Original post by asinghj)
    Reaction mechanisms
    Spectroscopy
    Bonding (intermolecular forces, etc)
    But 3 get 1 free:
    Physical trends
    thanks
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    (Original post by maxross)
    how did they mess it up?? what was wrong with it
    pi- + proton -> K0 + X
    The interaction was strong so strangeness conserved
    We had 4 options 2 were
    C: 0, B: 1, S:-1
    C: 0, B: 1, S: 1

    Now both could be right as K0 could be down andtistrange or strange andtidown so both options were correct
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    (Original post by asinghj)
    pi- + proton -> K0 + X
    The interaction was strong so strangeness conserved
    We had 4 options 2 were
    C: 0, B: 1, S:-1
    C: 0, B: 1, S: 1

    Now both could be right as K0 could be down andtistrange or strange andtidown so both options were correct
    haha jesus AQA. Hope we don't get that today
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    (Original post by 4nonymous)
    All you have to remember for termination is that you just put two radicals together.
    Although could you also do:
    CF2Cl• + Cl• -> CF2Cl2?
    Maybe some others?
    Although they don't tend to ask you for all the termination steps, usually just one or two so should be fine
    Ok thanks that's fine
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    (Original post by maxross)
    haha jesus AQA. Hope we don't get that today
    OCR won't do that
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    (Original post by asinghj)
    Ok so just wanted to confirm if this random example is right

    Initiation :
    CF2Cl2 -> CF2Cl• + Cl•

    Propagation:
    Cl• + O3 -> ClO• + O2
    ClO• + O -> Cl• + O2

    Termination:
    Cl• + Cl• -> Cl2
    CF2Cl• + CF2Cl• -> C2F4Cl2

    Did I miss anything out? Also should there be a 3rd termination?
    Not sure if you would include Cl radical and ClO radical as it is an intermediate but I guess so
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    (Original post by Jitesh)
    Yeah just write it out a couple times

    For ozone depletion, Cl and NO radicals are the main ones they ask about

    CFCs split by homolytic fission to form a Cl radical (depends what they give etc)... it's the Cl itself that's mainly responsible rather than the other radical formed

    E.g. CF3Cl -> CF3 Radical and Cl Radical (under UV)
    Yep got it now. Just going over mechanisms now. Is nucleophilic a heterolytic fission?
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    Is shapes of molecules likely to come up?
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    (Original post by Cherx)
    Yep got it now. Just going over mechanisms now. Is nucleophilic a heterolytic fission?
    yes, free radical substitution is homolytic
    electophilic addition and nucleophillic substitution are heterolytic
 
 
 
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