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    (Original post by MrProff)
    There was some stuff on that crazy long chemical..Sodium Hydrogenethanedioic acid maybe?

    I think with that the thing was it would have only donated one H+ in equilibria cos the other side was a methanoate group so wouldnt have affected it?
    Yes it is and if u use dioic u will have two H+ donated. So u have to times H+ conc by two which would not be right coz that acid is weak so it dissociates only slightly hence we would be overestimating the pH

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    (Original post by AS01)
    Yes it is and if u use dioic u will have two H+ donated. So u have to times H+ conc by two which would not be right coz that acid is weak so it dissociates only slightly hence we would be overestimating the pH

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    Seems about right! :^_^:
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    (Original post by MrProff)
    Seems about right! :^_^:
    Did u get first order and Ea as 38kJmol-1?

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    (Original post by AS01)
    Did u get first order and Ea as 38kJmol-1?

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    on the last question?
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    (Original post by MrProff)
    on the last question?
    Yeah

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    I got around 414000 Jmol-1 so yeah 41.4KJ but its all down to gradient so seems right
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    (Original post by MrProff)
    I got around 414000 Jmol-1 so yeah 41.4KJ but its all down to gradient so seems right
    Cool! Btw that dioic acid was asking us to compare with salt right? Rather than ethanoic acid

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    Well that was a strange exam, the entropy questions were nice and the pH stuff was alright. Not too sure I liked all the mechanism stuff though.
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    (Original post by HarryMWilliams)
    Well that was a strange exam, the entropy questions were nice and the pH stuff was alright. Not too sure I liked all the mechanism stuff though.
    Ikr! That paper was weird!

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    (Original post by AS01)
    Ikr! That paper was weird!

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    Frankly, I would have prefered to have done the Jan 2013 paper again.

    What "method" did people put for the Section C question about measuring the concentration of iodine and why was the S2O82- in excess?
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    (Original post by HarryMWilliams)
    Frankly, I would have prefered to have done the Jan 2013 paper again.

    What "method" did people put for the Section C question about measuring the concentration of iodine and why was the S2O82- in excess?
    Same! Colorimetry and it's coz it reacts with iodine and gives better result coz it makes sure that if iodine which is present in more amount than the conc of thiosulphate then the solution changes color straight away. I didnt write this lol I asked my teacher and she said that's what is thiosulphate for

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    (Original post by AS01)
    Same! Colorimetry and it's coz it reacts with iodine and gives better result coz it makes sure that if iodine which is present in more amount than the conc of thiosulphate then the solution changes color straight away. I didnt write this lol I asked my teacher and she said that's what is thiosulphate for

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    Ah, I thought about colorimetry and then just went with a running titration (stupidly) after I thought the first example was a colorimtry experiment.

    I said it had a much high concentration/volume so it was in excess and didn't act as a limiting factor during the experiment.
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    (Original post by HarryMWilliams)
    Ah, I thought about colorimetry and then just went with a running titration (stupidly) after I thought the first example was a colorimtry experiment.

    I said it had a much high concentration/volume so it was in excess and didn't act as a limiting factor during the experiment.
    It was iodine clock reaction
    Yeah I thought the same I even put it donates S2O3 2- ion but then later I was like no! That doesnt make sense! And wrote something about precise colour and all but I wrote it reacts with IODIDE ion!!!!!

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    (Original post by AS01)
    Cool! Btw that dioic acid was asking us to compare with salt right? Rather than ethanoic acid

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    Im not sure, pretty sure it was though!

    (Original post by HarryMWilliams)
    Frankly, I would have prefered to have done the Jan 2013 paper again.

    What "method" did people put for the Section C question about measuring the concentration of iodine and why was the S2O82- in excess?
    I put colorimetry because it said without sampling, so that means you couldn't do a titration right?
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    has anyone done an unofficial mark scheme?
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    (Original post by MrProff)
    Im not sure, pretty sure it was though!



    I put colorimetry because it said without sampling, so that means you couldn't do a titration right?
    Yeah, I should have stuck with my initial reaction in all honesty.

    http://www.thestudentroom.co.uk/newr...ply&p=43131557

    If I can get a copy of the paper then we can try.
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    Could the grade boundaries for a B possibly be below 60/90 ?
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    The second mcq, the one that asked why 2 methyl propanoic acid had lower entropy, was it a? Because it had lower bp?

    Also, I wrote units for activation energy as J :s will I lose marks because I didn't write j/mol?




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    (Original post by randyaloul)
    The second mcq, the one that asked why 2 methyl propanoic acid had lower entropy, was it a? Because it had lower bp?

    Also, I wrote units for activation energy as J :s will I lose marks because I didn't write j/mol?




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    I think it was more ways of distributing energy or whatever. Because that's what entropy is all about... the most disorder or in other words the most ways of distributing energy

    Sorry, I think you would... they did specifically ask for units. I really screwed that one up I think I got 500 something...
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    (Original post by randyaloul)
    The second mcq, the one that asked why 2 methyl propanoic acid had lower entropy, was it a? Because it had lower bp?

    Also, I wrote units for activation energy as J :s will I lose marks because I didn't write j/mol?




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    Umm u might. Look on other paper where they asked to work out Ea and see if they penalise u for wrong unit.

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