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AQA Chemistry Module 3 watch

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    (Original post by imasillynarb)
    Good, thats what I put, phew. I cant remember anything particularly challenging in that exam really, all bloody straightforward...
    Indeed. Let's hope enough idiots took it that the grade boundaries aren't too high. The mechanisms were a doddle.
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    (Original post by xskater)
    i put 2-methylbutane as the question related to CATALYTIC cracking rather than thermal
    At the end of the day, it said 'Draw a possible structure of an alkane with molecular formula C6H12' ...I did, so Ill get the marks
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    (Original post by kingpong)
    Indeed. Let's hope enough idiots took it that the grade boundaries aren't too high. The mechanisms were a doddle.
    Oh, what did you put for the 'type of alcohol' for propan-2-ol ? I put secondary, is that right?
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    yeah it's secondary.......i got a little muddled with carbocations (being 1st 2nd and 3rd).....but yeah it's a secondary
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    (Original post by imasillynarb)
    At the end of the day, it said 'Draw a possible structure of an alkane with molecular formula C6H12' ...I did, so Ill get the marks
    True, but like I said before, just plain old alkanes weren't listed in the products of catalytic cracking in that little box thing on the diagram. I dunno, it'd be tough if you weren't given the mark, since alkanes are a product.

    The thermal cracking question was the biggest piece of piss, same as the bromine free radical substitution question.
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    (Original post by imasillynarb)
    Oh, what did you put for the 'type of alcohol' for propan-2-ol ? I put secondary, is that right?
    Course.
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    (Original post by xskater)
    yeah it's secondary.......i got a little muddled with carbocations (being 1st 2nd and 3rd).....but yeah it's a secondary
    There was a question regarding primary and secondary carbocation if i remember right, something about major and minor products. That was pretty simple too.
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    For the thermal cracking question, I didnt know the mechanism, I just said it works by the homolytric fission of C-C bonds :/
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    anyone think they can outline FOUR points for the fractional distillation question ?
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    (Original post by xskater)
    anyone think they can outline FOUR points for the fractional distillation question ?
    Longer chains have higher boiling points, more VDW's
    Negative temperature gradient on the column
    Fractions seperated based on different boiling points

    yada yada, explain process etc...
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    (Original post by xskater)
    anyone think they can outline FOUR points for the fractional distillation question ?
    I just said, vaporised crude oil is passed into the fractionating column. The column is hotter at the bottom than at the top, and therefore has a negative temperate gradient. I said that there are trays at different points in the column, which are therefore at different temperatures. When the crude oil fractions reach a sufficiently cool tray they condense and are piped off. Therefore lower Mr fractions which have lower boiling points are piped off nearer the top of the chain...
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    (Original post by imasillynarb)
    For the thermal cracking question, I didnt know the mechanism, I just said it works by the homolytric fission of C-C bonds :/
    I put free radical, it's what it said in my book.
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    (Original post by imasillynarb)
    I just said, vaporised crude oil is passed into the fractionating column. The column is hotter at the bottom than at the top, and therefore has a negative temperate gradient. I said that there are trays at different points in the column, which are therefore at different temperatures. When the crude oil fractions reach a sufficiently cool tray they condense and are piped off. Therefore lower Mr fractions which have lower boiling points are piped off nearer the top of the chain...
    top of the column even
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    I learnt all the fricken fractions and their uses for nothing.

    Ptuh.
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    sounds good you guys.....i had SO MUCH TIME i wacked down a massive half page essay with a shed load of points hoping to catch 4.

    i hate them kinda questions...you know the aswer but can lose easy marks if your not careful what you put down
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    (Original post by kingpong)
    I put free radical, it's what it said in my book.
    My book didnt say anything about the intermediate, ****ing thing, so I just put what it did say ie. homolytic fission
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    (Original post by kingpong)
    I learnt all the fricken fractions and their uses for nothing.

    Ptuh.
    Same, so much stuff didnt get tested, quite disappointing really!
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    (Original post by imasillynarb)
    My book didnt say anything about the intermediate, ****ing thing, so I just put what it did say ie. homolytic fission
    I think that should be alright, mine said it was a homolytic fission/free radical anyways. Since I dunno what the feck homolytic fission is, I didn't put it.
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    (Original post by imasillynarb)
    For the thermal cracking question, I didnt know the mechanism, I just said it works by the homolytric fission of C-C bonds :/

    i've seen that question on another paper...and the examiners allowed homolytic fission. you should get the mark !!!


    Homolytic fission is the break of a covalent bond to PRODUCE free radicals. Which is quite similar to how thermal cracking works !!
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    (Original post by imasillynarb)
    Same, so much stuff didnt get tested, quite disappointing really!
    I was actually a little pissed at how easy the paper was. I'd worked my balls off for it so I was at least hoping for a semi-hard paper that would at least knock the grade boundaries down a bit. Anyways, you win some you lose some.
 
 
 
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