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    How has everyone learned the colours and equations?
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    (Original post by lahigueraxxx)
    http://filestore.aqa.org.uk/subjects...5-QP-JUN13.PDF

    http://filestore.aqa.org.uk/subjects...W-MS-JUN13.PDF

    I spoke too soon when I said I like the titration questions... would someone please send me a worked through example of 8c?? I'm lost Thank you in advance
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    (Original post by SirRaza97)
    I thought you couldn't round to 3 and had to say 1:2.9?
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    (Original post by SirRaza97)
    Omg that makes sense!! Thank you so much, I really appreciate it
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    (Original post by ravichauhan11)
    I thought you couldn't round to 3 and had to say 1:2.9?
    I don't know but you can't have .9 of a chlorine atom so I rounded it to 3.
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    (Original post by The Informant)
    How has everyone learned the colours and equations?
    Reading them and remembering them (y)
    Remember all of Fe(iii) is brown.
    Fe(ii) is green
    Cr(iii) is green except [Cr(nh3)6]3+ which is violet
    Al(iii) is colourless except Al(H2o)3(oh)3 is a white ppt
    Copper is always blue except dark blue in [cu(nh3)4(h2o)2]2+ and yellow green CuCl4^2- and green blue CuCO3
    Co is pink then blue in oh- , straw in ammonia.. Brown when oxidised..
    That's about it tbh...
    Oh but also orange Cr2o7 and yellow CrO4..
    And yellow Co3+
    Not too much really
    And also Cr2+ is blue
    And MnO4- is purple


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    (Original post by Suits101)
    Yes with E values

    Platinum is used if a half-cell does not contain a metal than can act as an electrode, where the metal MUST be a SOLID. This is when Pt is indicated on the outside of conventional cell diagram.

    E.g:

    Fe2+ + e- -> Fe+
    In this example, the metals in this half-cell are not solid because they are ions, hence you do not have a metal that can act as an electrode which is why a platinum electrode is necessary:
    Pt | Fe+, Fe2+ ||

    Zn2+ + 2e- -> Zn
    In this example, there is a metal that can act as an electrode (Zn) because it is a solid, hence a platinum electrode is not necessary: Zn | Zn2+ ||
    Awesome. Cleared that one up nicely for me. Sorry for such a late reply I have been revising for Core 3 which is tomorrow morning!!!
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    (Original post by chzm)
    Pt|H2(g)|OH–(aq),H2O(l)||O2(g) |H2O(l),OH–(aq)|Pt
    is this the same thing even if you swap the OH and the H2O over at the end as this is what the mark scheme states
    Yes, since oxygen has an oxidation state of -2 in both OH- and H2O, although there should be a vertical line between OH- and H2O because they are in different phases. A comma is used to separate species in the same phase, such as Fe2+(aq), Fe3+(aq).
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    (Original post by ravichauhan11)
    I say purple but there are many alternatives
    (Original post by 26december)
    I have always learned it as yellow but you could say either


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    Ok thanks
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    (Original post by Jpw1097)
    Yes, since oxygen has an oxidation state of -2 in both OH- and H2O, although there should be a vertical line between OH- and H2O because they are in different phases. A comma is used to separate species in the same phase, such as Fe2+(aq), Fe3+(aq).
    thanks, i copied this off the mark scheme though and i think you put a comma even it is (aq) and (l) because essentially theyre both liquid
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    H2O2 + 2e– 2OH–
    2[Cr(OH)6]3–+ 3H2O2 2CrO42–+ 8H2O + 2OH–

    can someone please explain how they got the overall balanced equation? its from question 7b ii in jan 2011 paper

    does anyone know what the half equatoin for the oxidation of [Cr(OH)6] to 2CrO4 would be in order to get the above overall equation as im struggling to come up with a balanced one

    thanks
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    (Original post by chzm)
    H2O2 + 2e– 2OH–
    2[Cr(OH)6]3–+ 3H2O2 2CrO42–+ 8H2O + 2OH–

    can someone please explain how they got the overall balanced equation? its from question 7b ii in jan 2011 paper

    does anyone know what the half equatoin for the oxidation of [Cr(OH)6] to 2CrO4 would be in order to get the above overall equation as im struggling to come up with a balanced one

    thanks

    [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
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    does anyone have a list of all the equations we actually need to learn?
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    (Original post by blueberry389)
    does anyone have a list of all the equations we actually need to learn?
    have a look on physicsandmathstutor.com chemistry revision section. They have a list there
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    How prepared are you all for tomorrow?
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    (Original post by TheTeresaLover)
    How prepared are you all for tomorrow?
    i havent started revision, since i have BIO5 the next day and ive been sick. But im not really worried, revised all of CHEM5 during the EMPA and i've been revising it and doing mocks on it for a while. From what i remember its pretty easy, with the ezpections of the colour od ligand sub.
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    (Original post by rimstone)
    i havent started revision, since i have BIO5 the next day and ive been sick. But im not really worried, revised all of CHEM5 during the EMPA and i've been revising it and doing mocks on it for a while. From what i remember its pretty easy, with the ezpections of the colour od ligand sub.
    I hope you are feeling well now
    Good luck for tomorrow and Thursday! If you don't mind me asking, what grades are you aiming for in chem?
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    (Original post by The Informant)
    How has everyone learned the colours and equations?
    Through repetition.

    There's no good mnemonics for the complex ions because there are just too many to remember - everybody has their own little methods. You are better off remembering which ions are 2+ (Cu, Co, Fe) and which ones are 3+ (Al, Cr, Fe) then remembering which ones have special reactions with NH3 (Cu, Cr, Co) and the ones that have special reactions with OH- etc.
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    (Original post by TheTeresaLover)
    I hope you are feeling well now
    Good luck for tomorrow and Thursday! If you don't mind me asking, what grades are you aiming for in chem?
    Yeah im a lot better now, have to revise anyway if im not.
    was aiming for a A, but the chances are that ill get a low B or high C after CHEM4. BIO4 was went so much better, if BIO5 is as easy, i should get an A easy, maybe even A*, which is the only consolations.
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    (Original post by rimstone)
    Yeah im a lot better now, have to revise anyway if im not.
    was aiming for a A, but the chances are that ill get a low B or high C after CHEM4. BIO4 was went so much better, if BIO5 is as easy, i should get an A easy, maybe even A*, which is the only consolations.
    Yes I agree with you. I was so confident about nailing CHEM4 but when I gave the paper I felt like killing myself! Let's hope tomorrow is not too hard! And yeah, BIOL5 better be good this time too! Lol!
 
 
 
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