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    hi hope someone can help me, i know how to draw a b/h cycle for lattice enthalpy of formation but how do i draw one for dissociation?

    eg q)1b from

    http://filestore.aqa.org.uk/subjects...W-QP-JAN11.PDF
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    (Original post by jonnyb123)
    Do we have to know all the colours of the 6 metal ions reactions with HCl? I know [CuCl4]2- is yellow and [CoCl4]2- is blue, that's the only two I've seen asked, but what are the rest of the colours for Fe2+, Fe3+, Cr3+and Al3+?
    we only need to know (cucl4)2- = yellow/green solution
    and (cocl4)2- = blue solution
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    Do we have to know about the reduction by zinc of some TMs
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    (Original post by ropin1)
    hi hope someone can help me, i know how to draw a b/h cycle for lattice enthalpy of formation but how do i draw one for dissociation?

    eg q)1b from

    http://filestore.aqa.org.uk/subjects...W-QP-JAN11.PDF
    Exactly the same but the arrow for lattice formation is the other way around- from solid ionic lattice to gaseous ions.
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    (Original post by SexyAndIKnowIt.)
    Do we have to know about the reduction by zinc of some TMs
    Only of Cr I think

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    (Original post by igobyursula)
    Only of Cr I think

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    I don't think I've learnt about this. What actually happens ???
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    (Original post by ropin1)
    hi hope someone can help me, i know how to draw a b/h cycle for lattice enthalpy of formation but how do i draw one for dissociation?

    eg q)1b from

    http://filestore.aqa.org.uk/subjects...W-QP-JAN11.PDF
    PI did this paper earlier and that is th only question I still don't understand even after looking at the marks scheme so if you figure out how exactly to use the numbers please let me know
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    (Original post by saba146)
    we only need to know (cucl4)2- = yellow/green solution
    and (cocl4)2- = blue solution
    Ok good, I thought so, where'd you find this out for sure? Is it somewhere in the book? (that we don't need to know the rest of them)
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    (Original post by SexyAndIKnowIt.)
    I don't think I've learnt about this. What actually happens ???
    This is the page in the nelson thornes. I can attach a pic of my notes from my teacher if your still unsure or if the textbook does not make sense.
    Name:  1371229800706.jpg
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Size:  78.7 KB

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    (Original post by SexyAndIKnowIt.)
    PI did this paper earlier and that is th only question I still don't understand even after looking at the marks scheme so if you figure out how exactly to use the numbers please let me know
    i figured a way of doing it, just do the born haber cycle as you would for lattice formation, but start your calculations from the left hand side, starting with your enthalpy of formation. and just remember if your going in the opposite direction to the arrows just use the opposite sign (+/-) for the values

    That gives the correct answer, hope this was clear enough?
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    (Original post by jonnyb123)
    Ok good, I thought so, where'd you find this out for sure? Is it somewhere in the book? (that we don't need to know the rest of them)
    http://filestore.aqa.org.uk/subjects/AQA-2420-W-SP.PDF
    pg 27 of the spec
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    (Original post by SexyAndIKnowIt.)
    PI did this paper earlier and that is th only question I still don't understand even after looking at the marks scheme so if you figure out how exactly to use the numbers please let me know
    You just draw one for the formation (if you need to ) and then flip the sign if you're asked for dissociation...
    Eg if the lattice formation of nacl is -1300 kjmol-1 then the dissociation is always +1300 jk mol-1


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    This question might not make sense but...

    There seems to be alot of manganate / dichromate half equations we need to learn for things such as titrations...
    do we have to learn them or do they give you enough detail to work them out in the exam? (for example i saw one which said hydrogen peroxide is titrated with acidifed pottassium manganate... hydrogen peroxide is reduced to oxygen gas), so is it always like that?
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    (Original post by Mocking_bird)
    This question might not make sense but...

    There seems to be alot of manganate / dichromate half equations we need to learn for things such as titrations...
    do we have to learn them or do they give you enough detail to work them out in the exam? (for example i saw one which said hydrogen peroxide is titrated with acidifed pottassium manganate... hydrogen peroxide is reduced to oxygen gas), so is it always like that?
    All the questions are different on what redox occurs, but they'll tell you what should happen, and then usually expect you to figure out the half equations and figure out the ratios from combining you equations. Like you example, H2O2 can also be reduced to 2OH- but they'll tell you which one exactly in the question, so you can do the rest, if that make sense?
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    Can't see what part you are referring to?
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    can anyone explain january 2012 question 8ei

    question paper http://filestore.aqa.org.uk/subjects...5-QP-JAN12.PDF

    mark scheme http://filestore.aqa.org.uk/subjects...W-MS-JAN12.PDF
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    Done 4 past papers now and the two most recent ones I've got what I need so that's pretty good. Just need to make sure I read the questions properly as I'm missing out questions or reading the question wrong.

    Need to go over redox/half equations again as I stuffed a lot of that up in the last one.
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    (Original post by jonnyb123)
    Can't see what part you are referring to?
    understand that the Cl− ligand is larger than these
    uncharged ligands and that ligand exchange can involve a
    change of
    co-ordination number
    (e.g. Co2+ and Cu2+)
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    (Original post by igobyursula)
    This is the page in the nelson thornes. I can attach a pic of my notes from my teacher if your still unsure or if the textbook does not make sense.
    Name:  1371229800706.jpg
Views: 184
Size:  78.7 KB

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    I've got this book already but don't understand really. Ill have a read
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    How is everyone learning all the transition metal colours / substitution reactions etc? Any tips?
 
 
 
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