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OCR A2 CHEMISTRY F324 and F325- 14th and 22nd June 2016- OFFICIAL THREAD watch

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    Do trans unsaturated fats have higher melting points because they pack closely together?
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    (Original post by tcameron)
    Do trans unsaturated fats have higher melting points because they pack closely together?
    yes more points of contact so stronger intermolecular forces require more energy to break
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    For H' NMR questions i sometimes find that the question includes, for example "this peak at 3.7ppm is usually found at 2.7ppm" do we need to know why the peak is further downfield/upfield than expected?
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    (Original post by qweening)
    yes more points of contact so stronger intermolecular forces require more energy to break
    (Original post by tcameron)
    Do trans unsaturated fats have higher melting points because they pack closely together?
    Thanks guys, keep forgetting to go over this. Is it just trans unsaturated or cis too or...? :s
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    (Original post by shamsaidk)
    can someone pls help me, the exams hours away and nothings sticking into my head and i can't even do a full past paper yet LOL
    hours away isn't it tomorrow afternoon
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    (Original post by tcameron)
    Do trans unsaturated fats have higher melting points because they pack closely together?
    Yeah

    Cis vs trans (polar vs non-polar)

    "Trans alkene has an organised structure, a packed structure due to which it has a higher melting point. Cis alkene has a higher dipole moment due to which it is more ionic, hence higher boiling point."

    Short answer:
    • cis is is polar, trans is non polar = cis has higher BP.
    • trans is more packed/structured = trans has higher MP.
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    (Original post by itsConnor_)
    Thanks guys, keep forgetting to go over this. Is it just trans unsaturated or cis too or...? :s
    cis unsaturated don't pack closely together but trans unsaturated do so trans have higher melting points than cis generally
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    yeah thats what i was referring to lOL
    (Original post by safhassan)
    hours away isn't it tomorrow afternoon
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    does anybody have any good tips on being quick on answering the paper? when i do past papers I normally just finish right as the hour is up and i never get a chance to check my answers
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    (Original post by Rust Cohle)
    Yeah

    Cis vs trans (polar vs non-polar)

    "Trans alkene has an organised structure, a packed structure due to which it has a higher melting point. Cis alkene has a higher dipole moment due to which it is more ionic, hence higher boiling point."

    Short answer:
    • cis is is polar, trans is non polar = cis has higher BP.
    • trans is more packed/structured = trans has higher MP.
    why would it be different for melting and boiling points though? Thought if melting point was higher so would the boiling point
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    Are my structures not right? ms is different bi)
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    (Original post by shanaj)
    does anybody have any good tips on being quick on answering the paper? when i do past papers I normally just finish right as the hour is up and i never get a chance to check my answers
    I believe f324 papers are now 1hr and 15 mins long
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    (Original post by Arima)
    I believe f324 papers are now 1hr and 15 mins long
    omg im such an idiot i did all the past papers in an hour lmao thanks
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    (Original post by tcameron)
    why would it be different for melting and boiling points though? Thought if melting point was higher so would the boiling point
    Not sure about the technical differences but shouldn't be a problem tomorrow. Don't recall even seeing a question on cis vs trans BP/MP anyways.
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    (Original post by lai812matthew)
    cuz it never came up in any papers before, and the exam board will try to catch people out with things that are never examined before. another thing i thought is how to distinguish a compound with stereoisomers and a compound without it. the answer is plane polarised light. and the racemic mixture thingy. it appears at AQA every year but never in OCR even though it is in the textbook!
    Nothing about racemic mixtures is mentioned in the spec so maybe that's why it hasn't come up
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    (Original post by lai812matthew)
    cuz it never came up in any papers before, and the exam board will try to catch people out with things that are never examined before. another thing i thought is how to distinguish a compound with stereoisomers and a compound without it. the answer is plane polarised light. and the racemic mixture thingy. it appears at AQA every year but never in OCR even though it is in the textbook!
    This is not examinable because it is not in the specification. Not everything in the textbook can be asked in the exam.
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    (Original post by itsConnor_)
    Are my structures not right? ms is different bi)
    It looks right to me. Same answer here




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    (Original post by Rust Cohle)
    It looks right to me. Same answer here




    what about my optical isomers, are they right? thx
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    (Original post by itsConnor_)
    what about my optical isomers, are they right? thx
    Yeah correct as well. Which paper is that by the way? Specimen? Because I've seen incorrect answers on them before
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    (Original post by Rust Cohle)
    Yeah correct as well. Which paper is that by the way? Specimen? Because I've seen incorrect answers on them before
    thanks phew
    AQA unit 4 june 2014
 
 
 
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