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    (Original post by OloMed)
    For the hexaqua complexes questions, there was something like cr(h20)6 3+ going to X(g) and Y(s). What was X(g). CO2?
    yep
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    what was the born haber oxide?
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    (Original post by Clarinet)
    The reaction was exothermic so if temperature increased, the reaction would shift to the left so solubility would decrease
    The reactiom was endothermic so the reverse argument.
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    Absolute dream of a paper, got 120UMS for sure - hope this has made a load of people who thought they did awful on CHEM4 feel a bit better, could be the paper that brings it back for them!
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    What equations did you guys write for each electrode in the hydrogen-oxygen fuel cell question?
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    (Original post by hi-zen-berg)
    Good shout. How many marks of 7 do you reckon would be obtained if the divide by 3 part is missed out, to give a % purity of 35.33 (what i got)?
    I did that too I think error is carred forward to an extent if I remember correctly (:
    (Original post by cowie)
    I said increase as would be a in increase rate of reaction - I don't think reaction was reversible so le chateliers principle would be irrelevant? May be wrong


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    The topic is called redox equilibria, of course le chateliers will be relevant.
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    (Original post by randoms132)
    I got an answer for 35% too


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    lol so did I
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    (Original post by K2Cr2O7)
    I put a straight horizontal line because there is a continuous supply of fuel. Anyone else put this ???
    I drew two lines and wrote a caption for each..
    One was horizontal and I mentioned fuel was constantly sullied
    The other was a curve with decreasing gradient and I mentioned this was when fuel was not constantly suplied


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    (Original post by Saldudsjen123)
    I did I'm such an idiot!! how many marks was that question?
    If I'm not wrong I think there was 2 1 mark questions? I did the same thing so annoyed, but thankfully the rest of the paper was decent


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    (Original post by zahraaj1)
    dissocation reactions are endothermic so the forward reaction is endo so the solubility increases when the temp increases as it shifts to the right (the endo reaction) because the solid ionic lattice (magnesium chloride) dissociates into its aqueous ions which increases the solubility. so idk how its a decrease haha
    Pretty sure dissocation is when it turns into gaseous ions, this was talking about aqueous ions, the enthalpy of solution was negative
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    (Original post by crillieswillies)
    Any idea how many marks I'd lose for getting delta G as -135000? I multiplied delta H by 1000 so delta H and delta S were in the same units :'(
    You were supposed to divide delta S by 1000 to convert from JK-1Mol-1 to KJK-1Mol-1
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    (Original post by crillieswillies)
    Any idea how many marks I'd lose for getting delta G as -135000? I multiplied delta H by 1000 so delta H and delta S were in the same units :'(
    Both are allowed...
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    me toooo
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    (Original post by Suits101)
    Half these because standard enthalpy means for one mole I believe (had to do it in a previous paper)

    Product is less disordered than reactants/product is more ordered than reactants
    It asked about the enthalpy change so I dont think you do it to one mole. I know the question you're talking about but that one had to specifically say 1 mole
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    (Original post by crillieswillies)
    Any idea how many marks I'd lose for getting delta G as -135000? I multiplied delta H by 1000 so delta H and delta S were in the same units :'(
    You lose none thats correct
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    did delta G have to be 3 sig figures???
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    For redox questions:

    Weakest OA: Zn2+
    Conventional cell diagram: Zn | Zn2+ || Co2+ | Co
    Half equation: Zn -> Zn2+ + 2e-
    Cobalt species: Co3+, oxidation product is oxygen, then reaction

    Negative electrode: H2 + 2OH- -> 2H2O + 2e-
    Positive electrode: 4e- + O2 + 2H2O -> 4OH-
    Overall reaction: 2H2 + O2 -> 2H2O
    Graph of emf: just a straight horizontal line
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    everyone remember to include that deltaH was approx 0 because same amount and type of bonds being broken and formed? for the thermo stability Q
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    Anybody making an unofficial mark scheme like for chem 4?


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    That was the nicest paper in the god damn world. Apart from the 7 marker calculation question it was so easy. Definite A*
 
 
 
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