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The Official Edexcel CH5 Revision Thread! (22/06/05 AM) watch

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    kpg ne chance of the Cr3+ q???...i knw its cheeky but desper8 times...
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    The oxygen of the water ligands form dative covalent bonds with the chromium (III) ion. There are covalent bonds between the oxygen and hydrogens. In terms of orbitals it's all here

    http://www.chemguide.co.uk/inorganic...hatis.html#top
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    any good past paper sites (except the thornbury college one)?
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    Naming complexes...how is it done??...dus the charge matter i.e. +ve or -ve ...
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    Does the Edexcel Unit 5 contain a synoptic element this year? Do you have a choice of questions?

    I see this has been the case in some previous years but what about the paper for Thursday?
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    If the overall charge is negative the metal ion will end in 'ate' with the exceptions of iron (ferrate) and copper (cuprate) e.g. chromium would be chromate

    If the overall charge is positive it stays as it is.
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    (Original post by kpg)
    -Benzene has a delocalised system of pi electrons, above and below a flat/planar benzene molecule. This stabilises the benzene molecule comparitivley
    -Electrophiles attracted to the delocalised pi electrons
    -When an electrophile reacts it forms a covalent bond with benezene on a carbon and the hydrogen is there too, this however disturbs the delocalised ring
    -Subst. happens rather than addition because it's energetically favourable for the hydrogen to be lost (pair of electrons back into the ring) and the delocalisation to be restored
    -Propene has a double bond : a sigma bond because of the overlap of s orbitals and a pi bond above and below the two carbons because of an overlap of p orbitals
    -When propene reacts the double bond breaks and two sigma bonds are formed which is energetically favourable

    Not explained very well but that's the general idea.
    thankz agen kpg...its just i just rote it out and it was about half a page in ma handriwttin...wat parts of it wud get u the 4 marks...the xam paper gave u 6 lines...sftee agen
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    (Original post by Islander)
    Does the Edexcel Unit 5 contain a synoptic element this year? Do you have a choice of questions?

    I see this has been the case in some previous years but what about the paper for Thursday?
    it is always 10% synoptic...i think that Section A B thing dnt happen nemore...its just a raw paper...not 2 sure bout the latter...verification ne1?
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    (Original post by kpg)
    If the overall charge is negative the metal ion will end in 'ate' with the exceptions of iron (ferrate) and copper (cuprate) e.g. chromium would be chromate

    If the overall charge is positive it stays as it is.
    [Co(H20)6]2+
    [Co(OH)6]4-
    wat wud the names b?? :stupido:
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    hexaaquacobalt(II)

    and hexahydroxycobaltate(II) maybe?
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    hexaaquacobolt (II) ion and
    hexahydroxycoboltate (II) ion ....i think
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    hey horray- must be doing something right!
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    nice 1 ppl
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    (Original post by mackin boi)
    thankz agen kpg...its just i just rote it out and it was about half a page in ma handriwttin...wat parts of it wud get u the 4 marks...the xam paper gave u 6 lines...sftee agen
    If it's 4/5 marks, usually something like :

    delocalised pi electrons in benzene (1)
    substitution reaction allows delocalised system to be kept (1)
    pi bond of alkene weaker than the bond in benzene (1)
    pi bond broken and two sigma bonds formed (1)
    more energetically favourable than substitution reaction (1)
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    sorted tahnkz
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    y is it still not lettin me rep u???
    also...is water ever in the rate equation??
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    (Original post by mackin boi)
    y is it still not lettin me rep u???
    also...is water ever in the rate equation??
    I shouldn't worry about it too much, ive never seen a question with this sort of complication.

    Kinetics question almost always have the equation given to you and a table of value for initial rate and the concentrations of the reactants. Then you just have to work out the orders. Apart from a couple of definitions, thats all i have seen.

    And even if it does come up, i seriously doubt water is include, since how do u find the concentration of water?
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    (Original post by KP Nuts)
    I shouldn't worry about it too much, ive never seen a question with this sort of complication.

    Kinetics question almost always have the equation given to you and a table of value for initial rate and the concentrations of the reactants. Then you just have to work out the orders. Apart from a couple of definitions, thats all i have seen.

    And even if it does come up, i seriously doubt water is include, since how do u find the concentration of water?
    I had a big debate about this with my teacher as she wasn't too sure of it herself, because I bought back my paper from january and they marked it wrong when I did not include water. You include water when it actually takes part in the reaction like with the reaction in the attachment, but usually you don't.
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    (Original post by mackin boi)
    it is always 10% synoptic...i think that Section A B thing dnt happen nemore...its just a raw paper...not 2 sure bout the latter...verification ne1?

    But why stick 10% synoptic in it when we have to do a whole synoptic paper as well?! I'm confuzzled.
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    dnno man...they probly tryin to get us prepped for it cos they knw its drrtttyyy...lol...
 
 
 
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