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Edexcel - Chemistry Unit 2 - 4 June 2013 Watch

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    (Original post by amber206)
    Why is there no hydrogen bonding between molecules of ethoxyethane? (Jan 2009, MC Q8)

    CH3CH2OCH2CH3
    Because no hydrogen atom is directly bonded to either (fluorine, oxygen or nitrogen).
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    (Original post by amber206)
    Why is there no hydrogen bonding between molecules of ethoxyethane? (Jan 2009, MC Q8)

    CH3CH2OCH2CH3
    Think about the structure, for hydrogen bonding to occur, hydrogen has to be bonded to a more electronegative element I.e. fluorine oxygen or nitrogen. Here in to molecule, hydrogen is only bonded to carbons which have very similar electronegativities. Because of hydrogen not being directly bonded to the oxygen, no hydrogen bonds form hope that helps
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    (Original post by own)
    Think about the structure, for hydrogen bonding to occur, hydrogen has to be bonded to a more electronegative element I.e. fluorine oxygen or nitrogen. Here in to molecule, hydrogen is only bonded to carbons which have very similar electronegativities. Because of hydrogen not being directly bonded to the oxygen, no hydrogen bonds form hope that helps
    It can form hydrogen bonds when dissolved in solvents (due to lone pairs on the central oxygen) however it cannot form hydrogen bonds with itself
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    If anyone has January 2009 CH02 to hand,
    the balancing of the half-equation for the
    reduction of dichromate ions?

    The electron number is 6 - why is it not 12?
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    (Original post by Goods)
    It can form hydrogen bonds when dissolved in solvents (due to lone pairs on the central oxygen) however it cannot form hydrogen bonds with itself
    Yes. I'm not quite sure what your getting at? The question taking about between molecules of ethoxylethane, not solvents.
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    I don't even know why I can't figure this out:The following reactions have been used in the chemical industry to make liquid and solid products, allowing any gaseous products to escape into the atmosphere:

    A CH3OH(g) + CO(g) --> CH3COOH(l)

    B CaCO3(s) --> CaO(s) + CO2(g)

    C CH4(g) + 3Cl2(g) --> CHCl3(l) + 3HCl(g)

    D CH2CH2(g) + Cl2(g) --> CH2ClCH2
    Cl(l)
    Which reaction causes the most immediate damage to the environment?
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    Anyones got jan 2013 paper unit 2??????
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    Did anyone do the June Unit 1 paper? And if so how did you find it and has anyone made an unofficial mark scheme for it?
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    Anyone know this one?? :/

    13 When solutions of iodine are titrated with aqueous sodium thiosulfate solution, Na2S2O3(aq),
    the thiosulfate ions are oxidized to

    A S2O4

    B S2O6

    C S2O8

    D S4O6

    all of these options are 2-
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    (Original post by Miri321)
    I don't even know why I can't figure this out:The following reactions have been used in the chemical industry to make liquid and solid products, allowing any gaseous products to escape into the atmosphere:

    A CH3OH(g) + CO(g) --> CH3COOH(l)

    B CaCO3(s) --> CaO(s) + CO2(g)

    C CH4(g) + 3Cl2(g) --> CHCl3(l) + 3HCl(g)

    D CH2CH2(g) + Cl2(g) --> CH2ClCH2
    Cl(l)
    Which reaction causes the most immediate damage to the environment?
    hmmmmm....i think it shud b C as HCL gas is produced which is a steamy fume so obviously the mst immediate effect cud b dat........though i;m little vague abt it...:erm:
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    (Original post by kevsamuel)
    Did anyone do the June Unit 1 paper? And if so how did you find it and has anyone made an unofficial mark scheme for it?
    I did that! it was a retake and i thought it was less harder than jan but still difficult... and ive been looking for the unofficial mark scheme as well... no luck so far
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    (Original post by lob.dub)
    Anyones got jan 2013 paper unit 2??????
    http://www.thestudentroom.co.uk/show...212573&page=10

    "Weaslemoose" posted two PDF's here.
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    (Original post by Miri321)
    I don't even know why I can't figure this out:The following reactions have been used in the chemical industry to make liquid and solid products, allowing any gaseous products to escape into the atmosphere:

    A CH3OH(g) + CO(g) --> CH3COOH(l)

    B CaCO3(s) --> CaO(s) + CO2(g)

    C CH4(g) + 3Cl2(g) --> CHCl3(l) + 3HCl(g)

    D CH2CH2(g) + Cl2(g) --> CH2ClCH2
    Cl(l)
    Which reaction causes the most immediate damage to the environment?
    Either B or C.

    B produces CO2 but C produces HCl.

    They clearly say 'most immediate effect' so I would go with HCl because it could acidify rivers and kill fish. CO2 on the other hand is a greenhouse gas and it takes time before it rises up into the atmosphere and traps heat energy emitted from the earth.
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    (Original post by Khurc003)
    I did that! it was a retake and i thought it was less harder than jan but still difficult... and ive been looking for the unofficial mark scheme as well... no luck so far
    Yeah, mine was a retake too as I got a C the first time round. I thought that it was easier than January too. But hopefully the grade boundaries will be at most about 63 for an A! (and that's pushing it...)
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    (Original post by amber206)
    If anyone has January 2009 CH02 to hand,
    the balancing of the half-equation for the
    reduction of dichromate ions?

    The electron number is 6 - why is it not 12?
    Dichromate has 2 chromiums at +6 and you are reducing it to Cr3+ to go from from 6 to 3 it is a gain of 3 electrons. Because there are 2 Cr's in dichromate you have to reduce both of them. therefore you needing 6 in total which equates to 3 electrons for each of the chromium's. hope that makes sense I'm resiting and doing the later units really helps with the earlier stuff.
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    (Original post by kevsamuel)
    Yeah, mine was a retake too as I got a C the first time round. I thought that it was easier than January too. But hopefully the grade boundaries will be at most about 63 for an A! (and that's pushing it...)
    yh that is pushing it.... lol I managed to scrap a B but right now im sooooo worried about unit 2 though timing is a big issue
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    Someone pleeeeasee help with this one

    When solutions of iodine are titrated with aqueous sodium thiosulfate solution, Na2S2O3(aq),
    the thiosulfate ions are oxidized to

    A S2O4

    B S2O6

    C S2O8

    D S4O6

    all of these options are 2-
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    (Original post by James A)
    Either B or C.

    B produces CO2 but C produces HCl.

    They clearly say 'most immediate effect' so I would go with HCl because it could acidify rivers and kill fish. CO2 on the other hand is a greenhouse gas and it takes time before it rises up into the atmosphere and traps heat energy emitted from the earth.
    Insanely stupid question.... does the atmosphere count as the environment ?

    I mean would you consider a factory and the atmosphere as being in the same environment.

    Also D won't react with the ozone will it ? only if it had a fluorine atom attached to one of the carbons it would? If so, do we need to know why this is..

    Thanks
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    Hi, Can someone please explain to me why chlorofluorocarbons are no longer used as fire retardants and why we use hydrocarbons and why doesn't it break down in the stratosphere?
    Thanks
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    (Original post by Khurc003)
    Someone pleeeeasee help with this one

    When solutions of iodine are titrated with aqueous sodium thiosulfate solution, Na2S2O3(aq),
    the thiosulfate ions are oxidized to

    A S2O4

    B S2O6

    C S2O8

    D S4O6

    all of these options are 2-
    It's D. It will always be D - it's just one of those 'factoids' you need to learn.
 
 
 
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