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F334 (19/06/2013 9:00AM) - Salters Chemistry (Chemistry of Materials) Revision Thread watch

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    (Original post by stealth_writer)
    Can someone please answer those above Q's please?
    Bump. No-one knows? exam is tomorrow guys.
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    Can someone please explain the whole of question 1h) on the june 2012 paper. Ill thumbs up you!!
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    (Original post by Waki)
    Could someone summarise zwitterions please
    just a molecule with both a positive charge and a negative charge- usually seen in amino acids where teh amine group protonates and the carboxylic acid deprotonates
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    (Original post by stealth_writer)
    Bump. No-one knows? exam is tomorrow guys.
    whats the question? if it was the end of jan 13 I'm going through the paper now :P
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    (Original post by billybobs)
    Look for C=O as this is the main functional group that is used to represent perm-dipole-dipoles. You are right in saying that there may be an electronegative atom present, but beware that if it is bonded to hydrogen it hydrogen bonds instead!
    thanks alot, I think I feel a abit more confident now :P Yeah I'm okay at recognising H bonds

    I've lost my AS book, can anyone summarise acid base titrations?
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    (Original post by Dude Ranch)
    Can someone please explain the whole of question 1h) on the june 2012 paper. Ill thumbs up you!!
    do you mean 2h?
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    (Original post by Tikara)
    whats the question? if it was the end of jan 13 I'm going through the paper now :P
    Well since your talking about Jan 13, then how do you do the following:

    Q2 b(ii), c(iii) (surely three moles are made?) and the very final question about rate of Iodine disappearing or what not

    cheers!
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    (Original post by Tikara)
    do you mean 2h?
    Yeah sorry 2h
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    Also guys... How do you dilution type Q's on these papers?
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    (Original post by stealth_writer)
    Also guys... How do you dilution type Q's on these papers?
    Any specific questions?
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    Help with Q 2 (b) (ii) please guys
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    (Original post by Dualcore)
    Any specific questions?
    Help with Q 2 (b) (ii) Jan 13 please
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    (Original post by Dude Ranch)
    Can someone please explain the whole of question 1h) on the june 2012 paper. Ill thumbs up you!!
    (Original post by Dude Ranch)
    Yeah sorry 2h
    h) i) from fiii we know that the ligand H2NCH2CH2NH2 is a bidentate ligand because the lone pairs on the nitrogens form 2 dative bonds(if you need more info on this let me know) in the question is gives the formula of the complex as [Cr(H2NCH2CH2NH2)3] so there are 3 ligands each forms 2 bonds with the Cr therefore the coordination number is 2x3=6. coordination number is the number of dative bonds to the central ion in the complex

    h) ii) and iii) not sure how to explain this but if you look at the mark scheme it might help. basically it just the normal octahedral shape with bond angle of 90 because there are 6 sets of electrons around the Cr however 2 of the bonds come from one ligand molecule/2 bonds are kinda linked. like a loop...

    h) iv) sorry i didnt understand this myself :/
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    (Original post by MTI)
    h) i) from fiii we know that the ligand H2NCH2CH2NH2 is a bidentate ligand because the lone pairs on the nitrogens form 2 dative bonds(if you need more info on this let me know) in the question is gives the formula of the complex as [Cr(H2NCH2CH2NH2)3] so there are 3 ligands each forms 2 bonds with the Cr therefore the coordination number is 2x3=6. coordination number is the number of dative bonds to the central ion in the complex

    h) ii) and iii) not sure how to explain this but if you look at the mark scheme it might help. basically it just the normal octahedral shape with bond angle of 90 because there are 6 sets of electrons around the Cr however 2 of the bonds come from one ligand molecule/2 bonds are kinda linked. like a loop...

    h) iv) sorry i didnt understand this myself :/

    Ah thanks so much its so simple now!
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    If a polymer is stronger, does it have a higher or lower Tg??
    Please can someone explain this too!!
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    Guys can someone help me out with jan 12 http://www.ocr.org.uk/Images/79818-q...-materials.pdf

    Q 1 d (iii) (iv).Im struggling with mathsy titration type Q's and its really frustrating.
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    (Original post by stealth_writer)
    Well since your talking about Jan 13, then how do you do the following:

    Q2 b(ii), c(iii) (surely three moles are made?) and the very final question about rate of Iodine disappearing or what not

    cheers!
    I'm stuck on the rate of disappearing too! I've never seen it come up before that paper...


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    (Original post by hannah1994)
    If a polymer is stronger, does it have a higher or lower Tg??
    Please can someone explain this too!!
    Higher, because the chains are closer together so form stronger intermolecular bonds
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    (Original post by Dude Ranch)
    Ah thanks so much its so simple now!
    glad someone else answered :P Just finished working through the question

    iv) is your stock enantiomer question - if it was monodentate then it wouldn't have this but due to the bidentate nature if you mirror the image it's nonsuperimposable (not the same when put on top of each other)

    my problems in that question were that I put diaminoethane rather than 1,2-diaminoethane
    and didn't know that electronegativity is only in a bond grrrr
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    (Original post by stealth_writer)
    Help with Q 2 (b) (ii) Jan 13 please
    I'll have a look now- but OCR number questions alllways catch me out but I'll have a go haha
 
 
 
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