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Cambridge Chemistry Challenge

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Reply 20
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 :s-smilie:


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'.
Reply 21
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 :s-smilie:


nope. look for the actual mole ratio
Reply 22
Roentgenium level question:
I get: "but what is x, what is y, what is z?"

No idea!
Reply 23
hmmm. have you worked out what the numbers mean?
Reply 24
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? :/
(edited 12 years ago)
Reply 25
not energy changes. what else in chemistry is in rows and columns?
Reply 26
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.
Reply 27
yup the periodic table and boiling points. that should be enough if you think about it.
Reply 28
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
Reply 29
Original post by Jack-

no problem
Reply 30
Any help for the gold question? Is the answer around 600000mL?
Reply 31
well right order of magnitude. quite a way off though. how have you worked it out?
Reply 32
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!
Reply 33
the moles of HCl are wrong i believe. and also the concentration 'molarity' of HCl at the end
Reply 34
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.
Reply 35
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 :smile:

EDIT: forget that! Solved it literally 5 minutes after posting this!
(edited 12 years ago)
Original post by Jack-

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...
(edited 12 years ago)
Reply 37
What is the answer for the gold question? I got 409725.262, but it doesn't work :frown:
Reply 38
new one out! :smile:
stuck on question 3 of the new one...

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