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    (Original post by OhNo_23)
    I have 2 questions which I was hoping somebody could help me with

    The melting point of aluminium oxide is lower than that of the other metal oxides because of the degree of covalent character it has (I don't really see how this means the bonding is weaker but I have given up trying to get my head around it!). However, further on it the textbook it says that one of the reasons aluminium oxide is insoluble is because of the additional covalent bonding which results in a stronger lattice. Isn't this contradictory?

    Also, is it the magnesium oxide or magnesium hydroxide that is sparingly soluble, or both?
    The first point I tried to tackle on page 9 (post number 162). But yes like Luke0011 said we don't need to know why at this level since you wont be asked to compare the melting point of the different ionic lattices.

    For your second point, I did a little digging because I wasn't sure either and it turns out both are insoluble.

    Mg(OH)2 is insoluble (as learnt in unit 2) and has a solubility in water of 0.012g per litre.

    MgO has a similar level of solubility in water of 0.086g per litre so I can say with quite a lot of confidence that it won't be soluble.

    To compare, NaOH (which is very soluble) has a solubility of 1110g per litre

    Then again this is coming from Wikipedia...
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    I'm still not over the bio AQA exam today but I'll do chem now. Forgotten everything though which is annoying. =/
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    (Original post by Sparkly-Star)
    I'm still not over the bio AQA exam today but I'll do chem now. Forgotten everything though which is annoying. =/
    At least we don't have to worry about all that HSW!
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    Can anyone explain this please: Ligand substitution with excess ammonia occurs in [Cr(H2O)6]3+. Why does ligand substitution with excess ammonia not occur in [Fe(H2O)6]2+ and [Fe(H2O)]3+? Thanks.

    And if I may ask, WHICH IS MORE ACIDIC: [Cr(H2O)6]3+ or [Fe(H2O)]3+ ?
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    (Original post by Supernovae)
    Ok, I should probably know this already, but I just wanted some clarification on electron shells.

    So when you fill up the electron shells, you fill up 4s first and then move onto 3d? (apart from the exceptions Cr and Cu) Yet when you write down the electron configuration, you write 3d first and then 4s?

    Also when an electron is removed to make an ion, is it removed from the 4s shell or the 3d shell?
    Yeah 4s before 3d, the other thing well that depends. If you look at the transition metals the way electrons are removed are not always followed by the same trend.
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    has anyone got the jan 11 MS please?
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    My revision for this starts at 5 pm tomorrow and ends at 9 am the next day

    Not good!
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    (Original post by cheeseisnice)
    What's the reaction with aluminum and sodium carbonate? I think my notes are wrong as they produce two (aluminum h20)6 instead of one
    Also do we need to know reactions with hcl?
    2[Al(H2O)6]3+(aq) + 3CO32-(aq) ? 2[Al(H2O)3(OH)3](s) + 3CO2(g) + 3H2O(l).. ...

    if your struggling with this topic i found this useful... http://www.a-levelchemistry.co.uk/AQ...5.5%20home.htm

    click on notes at the top of the page
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    guys i dont understand redox i need some help i understand the basics but not properly anyone knw any good revision sites
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    (Original post by Supernovae)
    Ok, I should probably know this already, but I just wanted some clarification on electron shells.

    So when you fill up the electron shells, you fill up 4s first and then move onto 3d? (apart from the exceptions Cr and Cu) Yet when you write down the electron configuration, you write 3d first and then 4s?

    Also when an electron is removed to make an ion, is it removed from the 4s shell or the 3d shell?
    Hey, I was wondering about this too, basically my book says when you make an ion the 4s electron are lost first.

    For example: Cu+ is 1s2 2s2 2p6 3s2 3p6 3d10 when Cu (1s2 2s2 2p6 3s2 3p6 3d10 4s1) is oxidised.

    The 4s1 electron is lost rather than an electron on the 3d orbital, (therefore Cu+ is not 1s2 2s2 2p6 3s2 3p6 3d9 4s1)

    Hope that helps
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    (Original post by InItToWinItGetIt?)
    has anyone got the jan 11 MS please?
    here it is
    Attached Images
  1. File Type: pdf AQA-CHEM5-W-MS-Jan11.pdf (202.6 KB, 47 views)
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    (Original post by Sparkly-Star)
    I'm still not over the bio AQA exam today but I'll do chem now. Forgotten everything though which is annoying. =/
    How was it?
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    Colours of transition metals? HEEEEELP!!
    Anyone got a list or a rhyme to remember them? Something!?

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    (Original post by hahaff)
    here it is
    Thanks
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    (Original post by T-Toe)
    How was it?
    worst than my worst nightmare
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    (Original post by hahaff)
    guys i dont understand redox i need some help i understand the basics but not properly anyone knw any good revision sites
    http://www.chemsheets.co.uk/

    thats got some pretty good stuff on, just scroll down a bit for CHEM5
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    (Original post by hahaff)
    worst than my worst nightmare
    It was wasn't it seems like everyone found it hard though so lets hope for low grade boundaries
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    how would you represent this as an electrochemical cell
    Zn(s) + 2H+(aq) --> Zn2+(aq) + H2(g)
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    (Original post by hahaff)
    worst than my worst nightmare
    OMgoodness I really hope you've done a lot better than expected. It's really bad how the exams for bio and chem5 are so close together. How's chem5 revision? Last year I knew nothing about chem5 so I studied using the CGP book the day before, did no past papers and came out with a D lol. I was actually quite chuffed at the time lol
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    (Original post by hey_its_nay)
    how would you represent this as an electrochemical cell
    Zn(s) + 2H+(aq) --> Zn2+(aq) + H2(g)
    Reduction on the Right.

    So
    Zn(s) | Zn2+ (aq) || H+ (Aq) | H2(g) | Pt(s)
 
 
 
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