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    (Original post by sportycricketer)
    For hydration it was -1941 or something like that did you multiply 2 by the hydration of Cl?

    And yeah I got that for Kc too.. quite weird to have an exact figure
    Yea I did
    I did
    Lattice entalpy + Enthalpy of solution = 2 x the hydration of Cl- + Hydration of Mg2+

    Then I had rougly
    -3000 = (2x -350) + Hydration enthalpy of Mg2+
    So I got around -2300

    These are just rough figures as I don't remember exact values
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    (Original post by Heatheroink123)
    Did anyone get uses for H2 as hydrogen fuel cell vehicles and margarine production? Or does anyone know if they're right?
    thats what I put too.
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    (Original post by KnuckleheadNinja)
    i swear the OCR guys this year must've been high when they wrote their papers. Hedgehogs and seaweed eating sheep in biology and now we've got willy wonka in chemistry with his magic tangy sweets.
    what next eh.
    :P
    the velocity of a falling OCR examioner from a cliff, i hope im be the one who'll be doing the pushing
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    (Original post by Rickesh)
    What did people write for the buffer question??
    Guys lets make the Unofficial Mark Scheme Mk1
    Please say if you have things to add, modify, or correct (theres lots!)

    ?)definition of lattice enthalpy: Energy given out when one mole of an ionic compound is formed from its constituent gaseous ions.[2]
    ?)Why is hydration enthalpy for Cl- exothermic? Bonds formed with deltaH+ on water molecules, heat given out.
    ?)Born Haber diagram of Enthalpy of solution, hydration, lattice enthalpy. 4 stages, incomplete answers: Mg2+(g) + 2Cl-(aq), Mg2+(aq) + 2Cl-(aq) [2]
    ?)
    ?)[Br] graph question. Marks for calculating 3 half lives, ~200s, stating that constant half life means its 1st order. State that methanoic acid in excess, so [methanoic] is constant and can be disregarded in the rate equation. calculate k, answer and units= ?? s^-1
    ?)
    ?)
    ?)
    ?)
    ?)Magic tang question: use lactic acid because its pKa is close to our desired pH (within one unit), so it buffers better. I used henderson hasselbach equation, pKa = pH + log [A-]/[HA] or you can use the ka expression to work out [A-]/[HA], which (I got) ~0.49
    I think it will be tangy because the buffering range (+/- 1 pH unit of pKa) certainly ecompasses the tangy pH of 3.55
    ?)
    ?)
    ?)H2 uses. The question asked for large scale usage, only two that immediately come to mind are H2 in hydrogenation of veg oils to produce margarine, and Haber process.
    ?)
    ?)
    ?)monomer unit for the complex ion polymer
    EDIT: JtKing3000 tells that they asked for the 4,4 version, not the 2,2 i've put up. He's right.
    ?)

    ?)

    ?)

    ?)

    ?)

    ?) % of Cu in Brass question
    Equations with state symbols:
    Cu (s) + 4HNO3 (l) --> Cu(NO3)2 (aq) + 2NO3- (aq) + 2NO + 2H2O
    Cu2+ + 2I- (aq) --> CuI (s) + 0.5 I2 (aq)
    2HNO3 (aq) + Na2CO3 (aq) --> 2NaNO3 (aq) + H2O (l) + CO2 (g)
    (one more which i can't rememebr)
    n(Cu) = 0.5n(I2) = n(S2O3)
    titre of 24.98 x 10^-3 cm^3 or summin, 0.1moldm^-3, n (S2O3)=that, so n(Cu) = 24.98 x 10^-3 cm^3
    so m(Cu) = nM = 24.98 x 10^-3 * 63.5 = 1.59 g of Cu in 2.8g or summin brass.
    % by mass= 67 point something percent, it asked to 1dp.
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    (Original post by Srai)
    I was kinda worried about the exam because I hadn't really done much revision, but it surprisingly wasn't that difficult.
    The topics were all ones that I remembered being taught, and the rest, I worked out intuitively - and some logical thought.

    Overall, I'd say not bad. Expecting 80%-90%.

    Also, this is science guys. It's not merely an exam. The questions weren't that difficult if you had been trained to think critically - though, that would not entirely be the fault of you, as most curriculums focus more on solving repititive sets of problems rather then thinking critically and applying what you know to more complex phenomena and context.
    douche.
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    (Original post by Amit619)
    Chances are they're fine. I wrote Haber and fuel cells
    Yes, Haber process and fuel cells. :cool:
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    (Original post by mathsmad)
    I completley agree.
    And what makes me think this even more is, my friends who resat the AS June unit this year.... said that exam was as easy as anything?! So are they going to try and give the AS's a false sense of security and think they are awesome at the subject so they will go to uni and pay too much?? The exams will go dead easy next year you watch.
    i dont get it.
    The exams are written years in advance, this had probably been written before the election had even happened!
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    (Original post by Kalamari Dave)
    Last two times it was ~60/100 raw marks for an A (120 UMS).
    For an A in the June 2010 paper it was 71/100 and 65/100 in the January 2011 so more ~70/100 for 120 UMS.

    Judging by general opinion I think it'll be the same as January give or take two marks.
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    (Original post by CoventryCity)
    Yea I did
    I did
    Lattice entalpy + Enthalpy of solution = 2 x the hydration of Cl- + Hydration of Mg2+

    Then I had rougly
    -3000 = (2x -350) + Hydration enthalpy of Mg2+
    So I got around -2300

    These are just rough figures as I don't remember exact values
    But if you remember the Solution for a minus figure therefore

    LE + (- Solution) + 750 = Hydration of Mg2+
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    (Original post by Heatheroink123)
    Well most people got 2.1 or something but I got 1.92/1.82 so I did something wrong somewhere. I hope I get marks for working
    I think i got 1.82 too

    How did everyone work out the pH? (For the Q with the acids in the table).
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    less than 50 for an a!!!!!!!!!
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    buffer question anyone??
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    (Original post by Dansat)
    Everyone needs to chill out, hard paper=low grade boundaries!
    Its not guaranteed. And even then some people may have REALLY messed up. Its not good enough for them.
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    (Original post by mathsmad)
    I completley agree.
    And what makes me think this even more is, my friends who resat the AS June unit this year.... said that exam was as easy as anything?! So are they going to try and give the AS's a false sense of security and think they are awesome at the subject so they will go to uni and pay too much?? The exams will go dead easy next year you watch.
    i dont get it.
    As aqa, ocr etc only do a-level qualifications it makes no sense for them to have easier or harder exams because they wont get any more money from student fees. Also, UMS will sort out any discrepancies derived from the difference in paper difficulty....
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    can anyone please pleassssssse upload the paper!!
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    (Original post by MoTheMedic)
    For an A in the June 2010 paper it was 71/100 and 65/100 in the January 2011 so more ~70/100 for 120 UMS.

    Judging by general opinion I think it'll be the same as January give or take two marks.
    Oops, talking about bio then :P
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    (Original post by Rickesh)
    buffer question anyone??
    I put something along the lines of "they may be able to emulate the sourness, but not the sweetness of that magic tang."
    One of the most bizarre questions I've seen.
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    i got 720 for kc
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    (Original post by blush.ox)
    I think i got 1.82 too

    How did everyone work out the pH? (For the Q with the acids in the table).
    10^-pKa = Ka

    Ka x HA = [H+]^2
    Get the value of [H+]
    Sub it into the pH formula and I'm almost sure that it said 2 dp for this qs
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    (Original post by sportycricketer)
    But if you remember the Solution for a minus figure therefore

    LE + (- Solution) + 750 = Hydration of Mg2+
    This is what I done

    Lattice enthalpy was around -2700 wasn't it and the enthalpy of solution around -300?
    -2700 - 300 + 750 = Hydration enthalpy
 
 
 
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