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OCR Salters Chemistry F335 12th June 2013 Exam revision thread Watch

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    Anyone got a copy of the paper?

    I'll even attempt the unofficial mark scheme if someone gets me it...
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    (Original post by badatgow)
    In the second line of the question I believe.
    I thought that was just the concentration, and had to manipulate it to work out moles.. but we weren't given a volume to calculate it? or was it literally the number of moles -_-
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    Hi everyone, I hope it all went as good as it could have done for all of you.
    Since I am the creator of this thread I will create a poll to see what the grade boundaries will be. Judging by your comments it seems like an average one. Should I add a numerical poll asking what the number for an A should be, or a qualitative poll? Asking how and or how good it went?
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    can anyone remember what the 'suggest the equation' question was? and what they put? there might have been two actually...
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    For the MMR of the compound did everyone go for the peak furthest to the right???
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    (Original post by badatgow)
    I found the paper overall pretty tough, but i'm confident i've done pretty well because I managed to finish quite fast and had plenty of time (like 40 mins) thankfully to check over everything a couple of times. While I was checking the paper I felt a lot better about my chances, because in hindsight most of the questions were relatively straightforwards. While doing the questions for the first time I felt like I was struggling a lot, but that's probably due to seeing unusual thinks like isoprenes etc.

    The interesting question IMO was the one about the calcium carbonate shells. My reasoning was that, increasing acidity increases [H+], so second equation equilibrium concentration shifts to the right. This increases concentration of [HCO3-]. I figured this would increase the concentration of [CO3 2-] in the first equation, so equilibrium would shift to the left to oppose the change. As a result, calcium carbonate concentration would increase and the shell thickness would increase. However, writing that down made me feel like a mug the entire time because i'm pretty sure if you pour acid on calcium carbonate it would just dissolve...but I couldn't see the chemistry to disagree with me. Oh well, only 2 marks if i'm wrong anyways.
    I totally agree! Why is that we are wrong if we did work backwards on that seashell Q?
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    (Original post by ActaNonVerba)
    I thought that was just the concentration, and had to manipulate it to work out moles.. but we weren't given a volume to calculate it? or was it literally the number of moles -_-
    nope it was just number of moles added (an excess). Some of it was unused (obviously) so here is the titration to calculate how much was unused.
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    How many marks was the mass spectrum part worth?
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    (Original post by stealth_writer)
    How many marks was the mass spectrum part worth?
    About five maybe.
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    (Original post by DoeADeer)
    Oh nooo, I multiplied it by 2 I think (((

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    i agree
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    (Original post by david2457)
    About five maybe.
    What did you get as the Mr of the compound?
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    (Original post by stealth_writer)
    What did you get as the Mr of the compound?
    32, and the compound I got it as CH3OH
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    The buffer pH question that involved the proportion of acid and salt changing was as follows:

    You were told enough alkali was added to react with half the acid in the previous part of the question (when salt/acid = 1/1). Therefore you essentially now have 1.5 parts salt and 0.5 parts acid, which simplifies down (1.5/0.5) to 3. Therefore to find pH you simply divided the Ka by three and found the -log.
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    (Original post by david2457)
    32, and the compound I got it as CH3OH
    Which was the peak furthest to the right??

    Correct.?
    How many marks was the CH3OH part worth?
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    (Original post by stealth_writer)
    Which was the peak furthest to the right??

    Correct.?
    Yes
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    (Original post by stealth_writer)
    Which was the peak furthest to the right??

    Correct.?
    correct
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    (Original post by david2457)
    Yes
    Where's the poll?
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    (Original post by badatgow)
    i'm not sure if it's correct but: Since we know the colour is "titanium yellow", and we know that the colour we see is the colour reflected i put a curve with maximum at the middle (yellow) going down to 0 at the red and blue ends.
    But the question said 93% reflectance at red and 90% green and 0% blue! So surely it shouldn't drop.
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    (Original post by Mattywooda)
    But the question said 93% reflectance at red and 90% green and 0% blue! So surely it shouldn't drop.
    i've got two peaks labelled red and green? how did you answer that question??
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    How many marks was the CH3OH part worth?
 
 
 
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