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

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    I got methylpropanoic acid?
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    (Original post by 4nonymous)
    Yh it would. Also I think for yield it was 67.4%
    As for the last question 43 peak does work with butanoic acid because its (CH3CH2CH2)+ ? Although I aint sure
    Fair enough. But how would you get a secondary carbocation in butanoic acid?
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    (Original post by Major Wilson)
    I got methylpropanoic acid?
    😐...

    Dang it.


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    (Original post by ronnydandam)
    it was 'in the first 200 secs' not at 200 secs I think
    I thought it said at. LOL we both "think"

    (Original post by asinghj)
    Check chemistry textbook page 148
    CBA - its done with now so who cares. Just glad chem is over with.
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    Did anyone say it was flammable so heat with electric heater under reflux
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    (Original post by Firenze26)
    Please tell me the last one about the mass spec question was Butanoic acid


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    I'm pretty sure it was. All the peaks (including 43) work fine with butanoic acid. I thought the mention of a secondary carbocation was just useless information - there isn't carbocations present in carboxylic acids anyway, only during reaction mechanisms right?
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    I put 67 percent to 2 sig figs do I lose any marks
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    (Original post by LordStark)
    I'm pretty sure it was. All the peaks (including 43) work fine with butanoic acid. I thought the mention of a secondary carbocation was just useless information - there isn't carbocations present in carboxylic acids anyway, only during reaction mechanisms right?
    I got methylbutanoic acid because I thought it would be able to make a secondary carbocation, but I dunno
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    (Original post by 11234)
    Did anyone say it was flammable so heat with electric heater under reflux
    That's the exact thing I wrote let's hope it's right! Haha


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    (Original post by torilee)
    I got that as well. I think that's the correct answer, but they'll probably give marks for butanoic acid as well, because it is an isomer of butanoic acid after all
    I think butanoic acid would be 5/6 marks because it clearly mentioned secondary carbonation
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    (Original post by Awsomedude)
    Mg was ionic I swear, it forms ionic bonds, not metllaic bonds.
    Wasn't talking about MgO, just the metal itself.
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    it was butanoic aCid
    you had TO times the EF C2H4O by two to get C4H802 OF WHICH THE MR WAS 88
    THERE WAS ALSO AN M/Z PEAK AT 88 SUGGESTING IT WAS BUTANOIC ACID
    IT COULDNT HAVE BEEN C2H40 SIMPLY BECUASE THAT ISNT A CARBOXYLIC ACID
    THE IR SPEC CLEARLY INDICATED IT WAS A C ACID
    THE MAS SPEC ALSO SAID THE MOST INTENSE PEAK WAS CAUSED BY A CARBOCATION WHICH WAS AT 43 OR 44
    SO THE MR WAS 88
    anyone agree?
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    (Original post by Tyler213)
    Fair enough. But how would you get a secondary carbocation in butanoic acid?
    Im not sure. I think it was methy-propanoic but I was just showing that you can have butanoic with that 43 m/z
    I put butanoic but oh well
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    (Original post by 4nonymous)
    Its metallic, ionic is between + and - ions metallic is between the + mg2+ ion and the delocalised electrons
    that's 2 marks down
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    A secondary carbocation meant that the positive charge had to be on a carbon that had 2 other carbons attached. So its not useless information, its actually vital.
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    (Original post by 11234)
    Did anyone say it was flammable so heat with electric heater under reflux
    what? no, I put use a pear shaped flask and condenser so the vapours dont escape from the top which they would in the way they showed it.
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    (Original post by Sophie7699)
    Yield was 67.4%
    Wasn't it 67.5
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    67 percent alright to 2sf yea? Maybe?
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    (Original post by asinghj)
    I think butanoic acid would be 5/6 marks because it clearly mentioned secondary carbonation
    Probably. I'm just conscious of trying not to scare people who'd thought it was really easy into thinking that they've failed or something
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    what did people write for the ozone depletion propagation steps?
 
 
 
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