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    (Original post by marleyxd)
    Then why do ionic lattices with covalent character have higher (more negative) latice formation enthalpies?
    they don't
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    (Original post by rommy123)
    can someone please explain the perfect ionic model?
    Ions are perfect spheres and it has no covalent character
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    (Original post by rommy123)
    can someone please explain the perfect ionic model?
    The perfect ionic model states:

    All ions exist as perfect spheres
    AND
    There are forces of electrostatic attraction between ions.

    This would be worth 2 marks ma if it were to appear, that's the answer, hope it helps.



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    (Original post by rommy123)
    can someone please explain the perfect ionic model?
    Basically it incinuates that all ions are perfect spheres with no distortion or covalent character so assumes they are purely ionic
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    Could someone please explain what the mark scheme means in question 6c, Jun 10? (http://filestore.aqa.org.uk/subjects...W-MS-JUN10.PDF)

    "(Delta S is negative so) at high tempt - T Delta S (is positive and) greater than Delta H

    So Delta G > 0"

    The actual calculation is easy but the above carries two marks
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    Is the positive terminal of a cell the anode or the cathode?
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    (Original post by BerryB)
    But it says excess ammonia. So shouldnt it form:
    [Al(NH2CH2CH2NH2)3]
    its not in excess
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    (Original post by BerryB)
    But it says excess ammonia. So shouldnt it form:
    [Al(NH2CH2CH2NH2)3]
    No. That would be an example of ligand substution. Ligand subsitution reactions can only occur with copper, chromium and cobalt.
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    (Original post by Med_me)
    Is the positive terminal of a cell the anode or the cathode?
    Anode is positive, cathode is negative.


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    hey.. can someone post the markscheme for the jan 13 chem 5?
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    (Original post by Med_me)
    Is the positive terminal of a cell the anode or the cathode?
    anode
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    (Original post by RoaringLion)
    Anode is positive, cathode is negative.


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    Thanks!
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    (Original post by MrMeep2580)
    anode
    Thanks, and is the oxidising agent found there?
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    (Original post by frogs r everywhere)
    No. That would be an example of ligand substution. Ligand subsitution reactions can only occur with copper, chromium and cobalt.
    Ohhh ok. thanks i get it now!!
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    (Original post by Brightbud)
    they don't
    Yes they do lol.... read p174 of nelson thorne
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    (Original post by frogs r everywhere)
    No. That would be an example of ligand substution. Ligand subsitution reactions can only occur with copper, chromium and cobalt.
    what, I didn't know this, why is that?
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    do we need to know how to work out Back Titrations?
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    (Original post by popnit)
    I know but I can't figure out why you put 2 moles!
    To balance the charge
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    Partial covalent character in an ionic lattic increases the lattice dissociation enthalpy. i.e. it takes more energy to break up the lattice.

    Why then, does Al2O3's partial covalent character make it have a lower melting point than MgO?
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    (Original post by Bootala)
    do we need to know how to work out Back Titrations?
    yes
 
 
 
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