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Equilibria, Energetics and Elements (F325) - June 2011 Exam. watch

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    (Original post by missred93)
    I got 2nd order aswell, because it didnt have a constant half life --the time went from around 190 to 400 which means it hasnt doubled = no constant half life?

    I may be wrong though?
    Yep, thats what I got too! Hopefully, we're right!!
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    (Original post by Rickesh)
    I didnt get that, nor did a few people I asked, they said its not a first order, as it didnt have a constant half life. when i worked it out i didnt get a constant half life?
    i got one of the half lifes diffrent to the other two but i stil said it was first order is that right?? i got 1 as 190 and the other 2 as 200 so i just said they had consatnt half life
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    (Original post by RodrigoB)
    so did I !!! but I heard in real life brass has approx 60% of cupper lol
    I did get 60 somethin %, and i know i few other people have
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    That was bull**** - my issue wasn't time it was that I didn't understand some of the questions; no matter how much time I spent thinking about them I couldn't do the buffer one and the final question.

    Why the **** was one of the marks asking to comment on the tanginess of sweets?
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    For the weakest acid to strongest acid thing, I got ethanoic as the weakest and pyruvic as the strongest. My method being the higher the pKa, the lower the Ka and the lower the Ka, the weaker the acid. Can anyone confirm this?
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    (Original post by Kalamari Dave)
    ARE YOU KIDDING ME??!
    I would switch grades with F215 from F325 anyday, I need F215 more and I almost certainly did better in this one.

    That ecology paper disguised as 'BIOLOGY' was absolutely disgusting and the spawn of the chief examiner in Hell, people at my school started to look at McD jobs and clearing!
    i revised ecology and engineering so much for that exam and was glad it was 95% ecology

    todays chem was the hardest exam ever. And i normally rape chemistry
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    Enthalpy of hydration = -2248 ? Or something like that?
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    Just looked up on wikipedia, and apparently brass typically has 60-70% copper content. Also, the two half equations for the decomp I put down seem to combine to make the correct equation, so I think this went pretty well. It was still tough as nails though.
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    (Original post by wbataylor)
    I did get 60 somethin %, and i know i few other people have
    i got 67 percent but i didnt divide the moles of sodium thiosulfate to work out moles of cu so i think i may get one or two marks as i caried my error foward
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    (Original post by susan23)
    someone came out of the exam saying...."aaaah I feel so good..."

    WHAT THE **** ARE YOU ON.
    Should've headbutted them

    (Original post by J DOT A)
    The reaction was feasible. I got like -100 something.
    Same.
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    (Original post by Kalamari Dave)
    It did I'm afraid, ~200s
    From the textbook:
    "A first order reaction can easily be identified from a concentration time graph. a first order reaction has a constant half life"


    The half lives were 190 then 210.

    Nowhere in the specification does it say "Half life is constant except sometimes when it's almost constant. It's still first order then."

    The half life was increasing. If the mark scheme only gives a mark for first order then that is ridiculous.
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    OCR ARE TAKING THE PISS! HAD TO SIT THROUGH JANUARY THAT WAS A WASTE OF TIME AND NOW THIS!

    WHAT A WASTE OF TIME, INK, MEMORY and PAPER!

    ANYBODY AGREE?
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    (Original post by student777)
    For the repeat unit I think you need:
    Complex ion with 4 waters and the weird ligand thing
    All inside square brackets with the charge
    All inside curly brackets (like in the question) with an n for the repeak unit
    I don't think you'll need curly brackets and the n, it said repeat unit not the formula.
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    (Original post by charlene_lamm)
    gotta revise for tmr's Maths C3.. and m already fed up with OCR..
    I have MEI mechanics tomorrow and judging by these OCR june papers so far it's not going to be easy
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    Does anyone have the paper?
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    (Original post by Vidja)
    From the textbook:
    "A first order reaction can easily be identified from a concentration time graph. a first order reaction has a constant half life"


    The half lives were 190 then 210.

    Nowhere in the specification does it say "Half life is constant except sometimes when it's almost constant. It's still first order then."

    The half life was increasing. If the mark scheme only gives a mark for first order then that is ridiculous.
    it also went back down to 200 after though.

    absolutely rancid paper. ocr are pulling them out this year.
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    (Original post by fredster2004)
    Does anyone have the paper?
    not till tomorow nooone will
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    Magic tang.. More make-believe science from OCR. Great!
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    i calculated the ph of both pyruvate and lactic acid, because i didnt know which one to choose..and i got 3.55 for pyruvate..but no one else seems to have written that..so im soooo confoooosed. maybe i didnt really work anything out, and my mind made me just wrtie 3.55??...if u want to know how i worked it out..we had pka, so i calculate ka..and then used that to calculate H+ conc...and then did -log(H+) which gave me 3.55...and also for the initial rate..i completely forgot how to draw a tangent! :/ i ended up getting 1*10-4 or something..is that completely wrong? and the last question..i had nooo idea what to do, cos we were only given one number..and i didnt know how to use it :'( oh deaaaaaaaaaar.
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    (Original post by Rickesh)
    Enthalpy of hydration = -2248 ? Or something like that?
    -1921 (you had to double the hydration enthalpy for cl-)
 
 
 
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