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Cambridge Chemistry Challenge

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ISA/EMPA exam discussion on TSR 05-03-2015
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    (Original post by lekha2611)
    Gold Q: Because it's 2 moles of gold for every 2 moles of HCl, do you just work out the moles of gold and carry the number across to use on the HCl - you don't have to divide it to find one mole? None of my figures are being accepted
    You're using the wrong ratios.

    Search aqua regia and refinement of gold. The equations should help you get the right ratios.

    Also, the number printed on the gold is of high importance. Just sayin'.
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    (Original post by lekha2611)
    Gold Q: Because it's 2 moles of gold for every 2 moles of HCl, do you just work out the moles of gold and carry the number across to use on the HCl - you don't have to divide it to find one mole? None of my figures are being accepted
    nope. look for the actual mole ratio
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    Roentgenium level question:
    I get: "but what is x, what is y, what is z?"

    No idea!
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    hmmm. have you worked out what the numbers mean?
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    Nope. At first I just tried finding a pattern - which I thought I had - but the numbers didnt work out. Melting or boiling points perhaps?

    Thinking about it, actually, energy changes looks like a possibility... but for what? :/
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    not energy changes. what else in chemistry is in rows and columns?
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    The periodic table? I'm sat looking at it, but nothing is coming to mind... I just can't think of any properties which would involve negative numbers, other than charge, which it clearly is not, and melting/boiling points in centigrade.
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    yup the periodic table and boiling points. that should be enough if you think about it.
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    (Original post by CM23925)
    yup the periodic table and boiling points. that should be enough if you think about it.
    Christ I cant believe I missed that for so long! I knew the 100 was intended to be the hint, and suspected it being a boiling point all along, but couldnt figure out the rest.

    Cheers for the help
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    no problem
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    Any help for the gold question? Is the answer around 600000mL?
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    well right order of magnitude. quite a way off though. how have you worked it out?
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    (Original post by CM23925)
    well right order of magnitude. quite a way off though. how have you worked it out?
    (250000/1000)*999 for the actual amount of gold
    Moles of gold by mass/mr
    Moles of Hcl by multiplying the gold moles by 6
    Then I got stuck, because I think you have to use molarity and I'm not sure what it is....
    If the molarity of HCl is 12, I just divided my answer by 12 and then multiplied by 1000 for mL, but clearly that isn't right! This question is annoying me so much!
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    the moles of HCl are wrong i believe. and also the concentration 'molarity' of HCl at the end
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    (Original post by education123)
    Are they boiling points of elements?
    Not quite, but the 100 is a pretty big clue. It is to do with the elements, yes, but in particular compounds.
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    I'm absolutely baffled on the roentgenium level question!

    I've also got the 'but what is x, what is y, what is z?' but apart from that, even with the hints people have given, I don't have a clue!

    I can see the link for getting the numbers at the bottom (if that has any significance), but as for the periodic table and boiling points, I'm not sure. Could someone please give a little more help? Please

    EDIT: forget that! Solved it literally 5 minutes after posting this!
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    (Original post by Jack-)
    Not quite, but the 100 is a pretty big clue. It is to do with the elements, yes, but in particular compounds.
    i get the whole 100 thing but don't quite spot the link
    maybe i'm just being stupid...

    Got it now...
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    What is the answer for the gold question? I got 409725.262, but it doesn't work
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    new one out!
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    stuck on question 3 of the new one...

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