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OCR Chemistry F322~ 4th June 2013~ AS Chemistry Watch

  • View Poll Results: How did you find the exam
    Hard A= 72
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    It was okay A= 76
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    Easy A= 79
    75
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    Very Easy A=82
    60
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    (Original post by geekD96)
    oh lord now im scared...could you give example for electrophilic then? thanks so much
    Only thing is, you have to remember what happens to some kinds of nucleophillic substiution reactions and their products for example adding concentrate ammonia (NH3) to fluouromethane (CH3F) makes CH3NH2 and hydrogen fluoride (HF). There are a couple of dodgy examples you need to know in nucleophillic substitution but they aren't that bad once you know them.
    The one with this example is that the NH3 isn't all added.

    CH3F + NH3 -> CH3NH2 + HF
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    (Original post by geekD96)

    aww you will be fine think positive ... to be honest I prefer afternoon ones...after lunch lol in the mornings I feel tired and hungry and sick
    Lol yeah I will be

    I just don't like em cause usually I get tired lol. When its in the morning I'm alert and what not!

    Thanks btw and good luck
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    (Original post by anonymousecheese)
    ok so its not my calculator...its me:confused:
    And me-.- Ive tried everything and gave up! I don't understand how to get it!
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    (Original post by IM_SCREWED)
    if from molecular to empirical is simplifying it, shouldn't it just be x ing it to get the molecular?
    if you have worked out the empirical formula and they want the molecular formula, they will give you the Mr of the molecular formula... so just do:
    Mr of molecular formula
    Mr of empirical formula
    the answer to this is what you multiply every atom in the empirical formula by, which gives the molecular
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    (Original post by Freyaa)
    I got the same I don't understand how to get the answer on the markscheme:/
    does anyone know how to get the answers in these questions?
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    (Original post by simifeltham)
    It is indeed but so are electrophilic addition reactions.

    you will only really come across homolytic fission in ozone depletion reactions or radical substitutions
    omg! that cleared so much up!!! thanks
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    (Original post by geekD96)
    nucleophillic=heterophilic...and electrophilic=homo? is this right
    No electrophilic addition is also heterolytic as one of the atoms has both of the electrons
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    (Original post by anonymousecheese)
    ok so its not my calculator...its me:confused:
    n=m/mr so 1x10^6/64.1=15600 part ii
    n=v/24 so 3.6x10^5/24 = 15000 part iii
    15000/15600 x 100 = 96% part iv
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    (Original post by Freyaa)
    And me-.- Ive tried everything and gave up! I don't understand how to get it!
    is this some enthelpy question ?
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    (Original post by Kits)
    Lol yeah I will be

    I just don't like em cause usually I get tired lol. When its in the morning I'm alert and what not!

    Thanks btw and good luck
    oh yeah..you too you prepared?
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    (Original post by simifeltham)
    n=m/mr so 1x10^6/64.1=15600 part ii
    n=v/24 so 3.6x10^5/24 = 15000 part iii
    15000/15600 x 100 = 96% part iv
    Thankyou so much!! I was being a pleb (a)
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    (Original post by Freyaa)
    Thankyou so much!! I was being a pleb (a)
    Your welcome
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    (Original post by opengeek)
    is this some enthelpy question ?
    Yes 1 e iii) on June 2010 paper
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    (Original post by Blashnet)
    omg thankyou!!

    So any radical has undergone homolytic fission?
    Radical Substitution is the ONLY mechanism or topic that involves homolytic fission.
    Addition and other substitution reactions are totally heterolytic!



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    (Original post by Freyaa)
    No electrophilic addition is also heterolytic as one of the atoms has both of the electrons
    may I just ask...that there is a nucleophillic addition and a nucleophillic substituition...are those different or same ;/ I think im overcomplicating myself
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    (Original post by simifeltham)
    n=m/mr so 1x10^6/64.1=15600 part ii
    n=v/24 so 3.6x10^5/24 = 15000 part iii
    15000/15600 x 100 = 96% part iv
    aah, thank you
    for some reason i get a different answer when i do 1.00x10^6 :mad:
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    (Original post by Freyaa)
    Yes 1 e iii) on June 2010 paper
    I remember that question it made me so angry ...the mark scheme was definitely talking rubbish ! no matter what i did i couldn't get the answer :/
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    I hope there is a question on explaining the effect of catalysts on the rate of reaction using enthalpy diagrams and the Boltzmann distribution...
    I'm on this ****
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    (Original post by geekD96)
    may I just ask...that there is a nucleophillic addition and a nucleophillic substituition...are those different or same ;/ I think im overcomplicating myself
    We weren't taught nucleophilic addition just nucleophilic substitution and electrophilic addition:/
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    Got a question for you guys.

    Explain what an exothermic reaction is in terms of bond braking and bond making (3 marks)
 
 
 
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