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    (Original post by Whangdoodle)
    I thought it was 120 and then 109.
    May be wrong though :P

    ALSO: I also thought that cycloalkanes and arenes are products of reforming. I put arenes.
    You are correct. Angle 'B' (first question) was 120 and angle 'A' was 109. Hence angle 'A' was smaller than angle 'B'.

    Arenes is also correct. Cycloalkanes would also have been right.
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    (Original post by Alivere)
    Just googled it and SiO2 is a giant covalent structure so each silicon would be bonded to two oxygen which each would be bonded to another silicon which would be bonded to another oxygen and so on damnnnnnn


    That video explains it. Well, I got this question wrong. Thank goodness it a 1 mark question.
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    Okay so grade boundaries will definitely be high, and if it's gonna be anything like the June 2012 one, the mark scheme will be very picky too.
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    I also wrote 'large complex network with covalent bonding' for the SiO2 q. doubt that would get me a mark, ugh.
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    (Original post by Problematique)
    Okay so grade boundaries will definitely be high, and if it's gonna be anything like the June 2012 one, the mark scheme will be very picky too.
    awww no don't say that :'(
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    Please someone do and unofficial mark scheme :'(
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    (Original post by EstebanK0)
    Here's what I did for the bond angle questions.

    Q. What is bond angle and shape for b? Explain your answer (4 marks)

    A. 120 degrees
    Planar Triangular
    3 areas of electron density around central C atom
    Electron repel as far apart from each other to overcome electron repulsion

    Q. Predict the bond angle for a and explain why.

    A. 109 degrees
    Has four areas of electron density
    did they ask for the shape as well ?
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    (Original post by nksunny)
    did they ask for the shape as well ?
    No, just bond angles. Though the MS might give a mark for shape... Who knows?
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    (Original post by dantdj)
    No, just bond angles. Though the MS might give a mark for shape... Who knows?
    I think it did ask for a shape for angle b (4 marker). That's how it's been for previous papers.
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    Unofficial mark scheme anyone please ??
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    I know this may sound like a silly question, but for the calculation questions provided you have the correct answer in the working out space, does it matter if you don't then re-write the answer in the space provided with the dotted lines they give? I'm having a stress that in my panic and rushing I forgot to do that and they might be really harsh and not allow it :eek:
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    hey guys i have the paper
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    (Original post by smileitsfree)
    hey guys i have the paper
    Really? Please be true.
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    I think the paper went very well, I have a question though about two questions which confused me only slightly ...

    One was the energy density one, I put 47,000. That threw me off because it asked for 2 sig. fig. and with a number that big I was doubting myself whether I did it the right way.

    Another one, which asked you about calculating enthalpy changes in a combustion reaction ... asking what other piece of information was needed to calculate it ..... I put something like "The mass of Hydrocarbon A that was burnt / used in the combustion reaction" .... other people were talking about Identifying the starting mass and final mass ... would I have got the mark for that question though?

    Looking at this thread though and talking to my teacher I think that is all that bothered me. So I think I have potentially lost 2-3 marks.
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    (Original post by Quiggle)
    Another one, which asked you about calculating enthalpy changes in a combustion reaction ... asking what other piece of information was needed to calculate it ..... I put something like "The mass of Hydrocarbon A that was burnt / used in the combustion reaction" .... other people were talking about Identifying the starting mass and final mass ... would I have got the mark for that question though?

    Looking at this thread though and talking to my teacher I think that is all that bothered me. So I think I have potentially lost 2-3 marks.
    I put down the mass of water. I can't even remember the layout of the question anymore.
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    (Original post by Quiggle)
    I think the paper went very well, I have a question though about two questions which confused me only slightly ...

    One was the energy density one, I put 47,000. That threw me off because it asked for 2 sig. fig. and with a number that big I was doubting myself whether I did it the right way.
    Did it definitely say to 2 significant figures?
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    (Original post by smileitsfree)
    hey guys i have the paper
    how?
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    (Original post by EstebanK0)
    I put down the mass of water. I can't even remember the layout of the question anymore.
    I have a feeling your answer may not be true, the first question we worked out the energy transferred to water, they gave us the volume of water ... I think they had us assume that 200cm^3 of water is equal to 200grams.

    (Original post by SherlockHolmes)
    Did it definitely say to 2 significant figures?
    Yes, definitely 2 significant figures and not decimal places.. I had to read it over 3 times just to make sure I wasn't being stupid

    The question gave us the energy density per mole, which was something like -5400 kJ mol^-1
    We are asked to find out the kJ per kilogram.
    We were given the Ar of the molecule, something like 112.

    So I found the amount of moles per kilogram .... 1000 / 112. Multiplied the moles by the value above (5400).
    Obviously these are rough estimates of what was given, I can't remember the exact values.
    But I would have got a value of about 47321, but below <47500.
    Then it asked for 2 sig fig. in the answer.
    The answer isn't a negative value as itis energy per kilogram and not an enthalpy change.
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    (Original post by Quiggle)
    The question gave us the energy density per mole, which was something like -5400 kJ mol^-1
    We are asked to find out the kJ per kilogram.
    We were given the Ar of the molecule, something like 112.

    So I found the amount of moles per kilogram .... 1000 / 112. Multiplied the moles by the value above (5400).
    Obviously these are rough estimates of what was given, I can't remember the exact values.
    But I would have got a value of about 47321, but below <47500.
    Then it asked for 2 sig fig. in the answer.
    The answer isn't a negative value as itis energy per kilogram and not an enthalpy change.
    Yes - that's the question. I did exactly the same method but for the answer I first put down 47321 then remembered to round for significant figures. And when rounding I did it to 3 significant figures instead of 2 for the answer 47300. Can't believe I didn't read that in the question
 
 
 
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