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    question 8c) january 2010 paper, can anyone post a solution?
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    (Original post by strawberry_cake)
    i did the jan11 a few weeks ago, not properly, just did a q, marked it, then the next as i had soo much other stuff to do and now have forgotten about it all btw can you help me with q 8c from the jan10 paper? I don't know which equations to use to see the ratio of the moles :/

    the titrations are annoying, i can do them but never know what to do for the last step when it wants the percentage or something...

    And i've just remembered that i still need to go through mod1 after i've been thorugh the syllabus :cry2:
    p4o10 + 6h20 ---4h3po4
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    for jan10 question 3c)
    is this correct as its different in the MS:
    Pt|OH-|H2|H2O|||O2|H2O|OH-|Pt
    with state symbols i know
    thankyouuuu any help appreciated¬!
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    (Original post by Rahul_V)
    when is a reaction feasible or spontaneous?
    reaction is feasible when ?s is large a positive, an ?H is negative and ?G Is negative.
    that's what we have been taught correct me if i'm wrong
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    (Original post by jwest)
    question 8c) january 2010 paper, can anyone post a solution?
    Credit to Sheldon

    http://www.thestudentroom.co.uk/atta...7&d=1308828134
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    (Original post by alimaahmed)
    reaction is feasible when ?s is large a positive, an ?H is negative and ?G Is negative.
    that's what we have been taught correct me if i'm wrong
    when delta G is negative
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    Thank you
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    (Original post by Mazii)
    It's an exothermic reaction as delta H is negativee
    The markscheme says otherwise :/
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    (Original post by kabolin)
    ewds
    ?? :confused:
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    (Original post by jwest)
    question 8c) january 2010 paper, can anyone post a solution?
    The way I did it (not 100% sure if this is the right way!):

    Know two equations for P4O10
    -P4O10 + 12NaOH -> 4Na3PO4
    -P4O10 + 6H2O -> 4H3PO4

    moles NaOH = 0.5 x 21.2x10^-3 = 0.0106 mol
    From equations, moles H3PO4 = 0.0106/3 = 3.53x10^-3 mol

    So moles P4O10 = 1/4 x 3.53x10^-3 = 0.883 mol

    Mr of P4O10 = 284

    mass = moles x Mr = 0.883 x 284 = 250.9 = 251 kg (3 s.f)
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    Does anyone have the link for the Jan 11 Mark Scheme?
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    (Original post by alimaahmed)
    reaction is feasible when ?s is large a positive, an ?H is negative and ?G Is negative.
    that's what we have been taught correct me if i'm wrong
    Just delta G negative i think
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    when do u put pt into the cell diagram?
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    (Original post by sophiakrywycz)
    any tips on learning colours fast?
    Learn all the easy ones:

    Fe2+ is generally green
    Fe3+ is purple, precitates go brown
    Cu2+ is generally blue
    Cu and Fe form yellow solution with Cl
    Cr3+ is generally green, remember titration, orange goes green, Cr2O7- ->Cr3+
    MnO4- is deep purple, Mn2+ is light pink (titration)
    Carbonates generally stay the same colour if bonded to 2+ ion, hydroxide formed 3+ ions.


    There are others you are required to learn, but these are the easy ones.

    Others include:
    Co2+ is pink solution, blue prec. in hydroxide, yellow in excess ammonia
    Co3+ is yellow, brown in hydroxide
    Cr3+ is purple in excess ammonia
    Cu2+ only allows 4NH3 around it, deep blue colour.
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    ahh mindblank, can anyone guide me through writing this representation



    using

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    Can someone plaese help me with my q pleasee
    paniking!
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    (Original post by alicetalbot)
    Does anyone have the link for the Jan 11 Mark Scheme?
    Yu shud find it on this page :
    http://www.a-levelchemistry.co.uk/AQ...ary%20home.htm
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    (Original post by OsmosisJones)
    Learn all the easy ones:

    Fe2+ is generally green
    Fe3+ is purple, precitates go brown
    Cu2+ is generally blue
    Cu and Fe form yellow solution with Cl
    Cr3+ is generally green, remember titration, orange goes green, Cr2O7- ->Cr3+
    MnO4- is deep purple, Mn2+ is light pink (titration)
    Carbonates generally stay the same colour if bonded to 2+ ion, hydroxide formed 3+ ions.


    There are others you are required to learn, but these are the easy ones.

    Others include:
    Co2+ is pink solution, blue prec. in hydroxide, yellow in excess ammonia
    Co3+ is yellow, brown in hydroxide
    Cr3+ is purple in excess ammonia
    Cu2+ only allows 4NH3 around it, deep blue colour.
    Thankyou so much for this, you're a star!!

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    (Original post by NRican)
    ahh mindblank, can anyone guide me through writing this representation



    using

    and me!
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    (Original post by cleo101)
    when do u put pt into the cell diagram?
    When there isn't a solid at the electrode
 
 
 
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