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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
    42
    15.22%
    It was okay A= 76
    99
    35.87%
    Easy A= 79
    75
    27.17%
    Very Easy A=82
    60
    21.74%

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    is everyones in the afternoon?
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    (Original post by reneetaylor)
    You're right! I'll include that definitely, thanks
    You can just say propene.
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    Can I have some predictions please guys?


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    (Original post by mari_lynne)
    hey guys could anyone help explaining to me bond enthalpy questions? when you have to work out the bond enthalpy of a molecule knowing normally the products and △H, would be so appreciated!
    Do you have an example of a question?
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    (Original post by ii-mohsin-ii)
    is everyones in the afternoon?

    I am assuming so.


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    (Original post by greenmind)
    Help urgently needed on how to answer question 6 from the Jan'12 paper
    Attachment 222839
    Attachment 222840

    Link to the markscheme is http://www.ocr.org.uk/Images/59185-m...es-january.pdf
    46
    CH2OH+
    C3H7O

    (63x72.2) + (65x27.8)
    __________________ = 63.6 which is CU
    100
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    (Original post by simifeltham)
    ch3ch2ch2oh ---->
    h2so4 reflux
    ch3ch2ch2oh + 2[o] -----> ch3ch2cooh + h2o

    CH3CH2CH2I + KOH------->
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    Say if you are given the molecular formula, how do you find the empirical formula from this? Thanks in advance
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    (Original post by greenmind)
    Help urgently needed on how to answer question 6 from the Jan'12 paper
    Attachment 222839
    Attachment 222840

    Link to the markscheme is http://www.ocr.org.uk/Images/59185-m...es-january.pdf
    i) m/z value of the peak furthest to the right
    ii) a formula which Mr adds up to 31, then just add + to end of that fragment (due to loss of electron)
    iii) compound containing C, H, O which Mr adds up to 46 (molecular ion value)
    b) (63x72.2)+(65x27.8)/100
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    can someone help meee... I just wanna know I get confused when it comes to curly arrows how do I know if its an nucleophile substitution or electrophilic.....please help thanks
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    (Original post by Hello...)
    ch3ch2ch2oh + 2[o] -----> ch3ch2cooh + h2o
    that would be k2cr2o7/h+

    with h2so4 and reflux it's dehydration so its CH3CH=CH2 + H2O
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    (Original post by geekD96)
    can someone help meee... I just wanna know I get confused when it comes to curly arrows how do I know if its an nucleophile substitution or electrophilic.....please help thanks
    If it involves adding things to a double bond to break the double bond, it's electrophillic
    It's nucleophillic if it involves swapping OH for a Halogen
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    (Original post by geekD96)
    can someone help meee... I just wanna know I get confused when it comes to curly arrows how do I know if its an nucleophile substitution or electrophilic.....please help thanks
    nucleophile is an electron rich species that can donate a lone pair of electrons such as OH-
    Electrophilic is the one such as the addition of HBr or Br2 across a double bond
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    (Original post by Ché.)
    Well!?
    113 would be around the mid/high 70s...
    120 is for an A; that will be around 80 or so...



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    Okay that's doable, thanks
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    (Original post by simifeltham)
    that would be k2cr2o7/h+

    with h2so4 and reflux it's dehydration so its CH3CH=CH2 + H2O
    Damn, just made the connection because H2SO4 is used in oxidising alcohols as well as K2Cr2O7
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    State four ways in which polymers are disposed?
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    (Original post by simifeltham)
    nucleophile is an electron rich species that can donate a lone pair of electrons such as OH-
    Electrophilic is the one such as the addition of HBr or Br2 across a double bond
    oh so if it gives us something like this (this is completely made up) ...................... c4h7I reacting with OH- to give C4H7OH+I- is electrophilic?
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    (Original post by Hello...)
    Damn, just made the connection because H2SO4 is used in oxidising alcohols as well as K2Cr2O7
    yeah that's why I always use just H+ on K2Cr2O7 so I don't get confused with other reactions
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    (Original post by CA$H KRAZE)
    Say if you are given the molecular formula, how do you find the empirical formula from this? Thanks in advance
    Empirical formula is just the simplest whole number ratio of the molecular formula... so an example of molecular formula... C3H6 simplifies down to CH2 but numbers that dont simplify down... C3H7 the molecular formula for this is the same as the empirical because it wont simplify without creating decimals
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    (Original post by geekD96)
    oh so if it gives us something like this (this is completely made up) ...................... c4h7I reacting with OH- to give C4H7OH+I- is electrophilic?
    C4H7I + OH- ---> C4H7OH + I- and it's nucleophilic because the OH- is an electron rich species due to the minus sign. it's negatively charged because it can donate a pair of electrons.
 
 
 
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