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    i come to this page after finishing my maths c3, which was stupid hard compared to 2015 backwards, knowing ive done no revision for this in the past 7 weeks due to being rimmed by as resits.i HOPE i can can remember all this in one day.

    if the papers as hard as chem4 ill eat my paper in the exam
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    (Original post by shamk123)
    i come to this page after finishing my maths c3, which was stupid hard compared to 2015 backwards, knowing ive done no revision for this in the past 7 weeks due to being rimmed by as resits.i HOPE i can can remember all this in one day.

    if the papers as hard as chem4 ill eat my paper in the exam
    lool this is literally me
    i need 100 in this paper or i've got no chance of a decent A after chem 4
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    What exactly do we have to know about metal extraction for this unit because I kinda forgot my AS stuff?


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    hi guys does anyone know how to get round thermodynamics im really struggling with it especially with the rearranging the born haber cycle ?

    thanks in advance
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    (Original post by The Informant)
    How has everyone learned the colours and equations?
    The only way you really can learn is through repetition - it gets very boring but on some past papers there have been like 12 marks for this section which can easily boost a grade!


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    (Original post by anonymous-97)
    hi guys does anyone know how to get round thermodynamics im really struggling with it especially with the rearranging the born haber cycle ?

    thanks in advance
    Try to remember that enthalpy of formation equals the rest of the cycle and then can work out the values and work out the differences


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    (Original post by 26december)
    Try to remember that enthalpy of formation equals the rest of the cycle and then can work out the values and work out the differences


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    when talking about [Al(oh)]4-, do you write it as that or as [Al(OH)4(H20)2]4- ?
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    (Original post by nutcase13)
    when talking about [Al(oh)]4-, do you write it as that or as [Al(OH)4(H20)2]4- ?
    It's not 4- it only has 1 minus
    [Al(H2O)2(OH)4]- with XS OH-

    For others though I always put 2+, 2-, 3+ etc. outside the bracket


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    (Original post by rolla01)
    [Cr(OH)6]^3– --> CrO4^2- + 2H2O + 2H+ + 3e- x2
    H2O2 + 2e- --> 2OH- x3

    these are the two half equations

    3H2O2 + 2[Cr(OH)6]^3– --> 6OH- + 2CrO4^2- + 4H2O + 4H+

    The OH- and H+ cancel out to make H2O, so 4H+ + 4OH- --> 4H2O
    3H2O2 + 2[Cr(OH)6]^3– --> 2OH- + 2CrO4^2- + 8H2O


    Hopefully this helped, if you still don't understand here is a useful link: http://www.chemguide.co.uk/inorganic...quations2.html
    brilliant thank you! i forgot that you can form water with the H+ and OH-
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    I think it is supposed to be [Al(OH)4(H2O)2]-. At least, that's how I've always written it.

    Also, I'm unclear on the 'why' of substitution reactions. For example, [Cu(H2O)6]2+ reacts with an excess of ammonia, it forms [Cu(H2O)2(NH3)4]2+. When my class asked our Chemistry teacher why that happens and why aren't all the H2O ligands replaced, all she said was "It just does". Can someone explain it, please??
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    (Original post by 26december)
    It's not 4- it only has 1 minus
    [Al(H2O)2(OH)4]- with XS OH-

    For others though I always put 2+, 2-, 3+ etc. outside the bracket


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    ah thanks
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    Does aluminium oxide or silicion dioxide have the higher melting point?
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    (Original post by thehollowcrown)
    Does aluminium oxide or silicion dioxide have the higher melting point?
    aluminium oxide
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    When they ask why a coloured ion is formed do you say the d-electrons absorb visible light or white light? I've always said it's visible light but then in one of the 2010 papers it said white light so now i'm not sure.
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    Can someone help me with bidentate ligands and M3+ ions? I assumed they would react in the same way as M2+ ions but according to http://filestore.aqa.org.uk/subjects...5-QP-JAN12.PDF Q8ei they don't. Why is this?
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    (Original post by shiney101)
    When they ask why a coloured ion is formed do you say the d-electrons absorb visible light or white light? I've always said it's visible light but then in one of the 2010 papers it said white light so now i'm not sure.
    I always visible light
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    Why are enthalpy changes approximate?
    is it because averages are used?
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    (Original post by shiney101)
    When they ask why a coloured ion is formed do you say the d-electrons absorb visible light or white light? I've always said it's visible light but then in one of the 2010 papers it said white light so now i'm not sure.
    i usually just talk about the visible light spectrum generally unless it tells u (or implies) in the question what colour it shows
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    (Original post by anonymous-97)
    hi guys does anyone know how to get round thermodynamics im really struggling with it especially with the rearranging the born haber cycle ?

    thanks in advance
    I explained it here before. It might help

    http://www.thestudentroom.co.uk/show...9#post65043249
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    Do we have to know how to name complexes?
    Lie tetrachlorocobalate (II)


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