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2016 IGCSE Chemistry Paper 2 Unofficial Mark Scheme 2016 Watch

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    (Original post by Nurne)
    C8H18 +8 1/2O2 -> 8CO2 + 9H20


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    was that after the isomer questions?
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    For the dot and cross diagram did u have to put 8 or 0 electrons on magnesium
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    (Original post by igggy)
    For the dot and cross diagram did u have to put 8 or 0 electrons on magnesium
    im pretty sure its 8 because its an ion, it has lost its 2 outer electrons to form the outer shell and formed a shell with 8 electrons.
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    Question 3 (?) 22.60, 22.45, 22.55 for the concordant results (numbers might be wrong, but they were boxes 2, 3 and 4)
    Add them up and divide by theee for average 22.53 (I think that was the average, cant be bothered to check)
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    (Original post by rcmack)
    was that after the isomer questions?
    Yup..


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    (Original post by Abodee1)
    im pretty sure its 8 because its an ion, it has lost its 2 outer electrons to form the outer shell and formed a shell with 8 electrons.
    Ok good thats what i did phew
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    For 4d I got CH3-CH2-CH2-CH2OH
    And 4e) -(-CH2-CHX-)-
    There was another molecule where the X is, but I cant remember its formula
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    For the question about the equation for incomplete combustion was the answer
    C8H18 + 6O2 > 6C + CO2 + CO + 9H2O
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    You need to add an extra ch2 to 4d. It was butanol not propanol.


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    (Original post by Nurne)
    C8H18 +8 1/2O2 -> 8CO2 + 9H20


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    It wasn't 8CO2 it was 8CO since incomplete combustion causes Carbon Monoxide to form instead of Carbon Dioxide, due to the lack of Oxygen.
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    Also there was a question about drawing the polymerisation of an alkene? What do you draw?
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    (Original post by Debby 123)
    It wasn't 8CO2 it was 8CO since incomplete combustion causes Carbon Monoxide to form instead of Carbon Dioxide, due to the lack of Oxygen.
    Sorry i meant 8CO carbon monoxide.


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    The isomer of but-1-ene was but-2-ene.
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    (Original post by rcmack)
    yea same, do you remember what question number that was?
    sorry, i dont
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    Yeah but I thought incomplete combustion causes some carbon monoxide and carbon to form, but also some water and carbon dioxide?
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    (Original post by iah1700)
    For the question about the equation for incomplete combustion was the answer
    C8H18 + 6O2 > 6C + CO2 + CO + 9H2O
    I got C8H18 + 8.5O2 -> 8CO + 9H20 (my friends agreed but we could be wrong)
    I think yours might also be correct, as it's the example given in the CGP revision guide, although I don't think it said anything about producing carbon in the question.
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    It is red. It said AFTER it has been neutralised
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    (Original post by Ashnii34)
    For the aluminium question was it 180g or 540g?
    I got 180g but some people say it's 540g
    I got 180g. 20 F of electricity = 3 moles of electrons. 3 moles of electrons: 1 mole of aluminium (from half equation given). 20/3 moles of aluminium made. Mass = moles × Mr = 20/3 x 27 = 180 g
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    (Original post by Ashnii34)
    For the aluminium question was it 180g or 540g?
    I got 180g but some people say it's 540g
    Defo 180


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    (Original post by Ashnii34)
    After it has been neautralised means it's neutral so it's orange
    Common misconception, it turns acidic


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