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# Cambridge Chemistry Challenge watch

1. (Original post by Silverland)
Rg is awful. You can spend hours on it and still struggle. Just a warning~!

(though Gold isn't that bad for an A2 chemist at all)
I agree, ive just spent over an hour on the Rg question and still havent got it :/
2. (Original post by Silverland)
in that searching the elements given all together will bring up links containing them and 3 others

it's just a dumb word game really though. Zilch chem
Got it. Worst question I've ever seen on this website.
3. how do we get the concentration of vinegar ions in gold
4. White wine vinegar is about 4-5% acetic acid, but I'm not sure if that helps.
5. Got Gold, make sure you give your answer to about 5 dp. Write out the Ka expression, that should help.
6. help on gold been stuck on it for years
7. Okay, Rg is hard. Could possibly use area density of graphene and circumference of a cylinder if I knew the diameter of the tube.
8. (Original post by Snakefingers13)
Okay, Rg is hard. Could possibly use area density of graphene and circumference of a cylinder if I knew the diameter of the tube.
Yeah, I've been having the same problem, how can we find out what diameter it is?
9. Can someone PM me gold? I'm soooo stuck
10. Can someone also PM me gold?
stuck is an understatement :c
11. Me too, I've been stuck on it for a while...
12. pm gold pleasssssssse
13. still stuck on entry level
help, hint, anyone
14. Look: Ka = [H+][X-]/[HX]

You know pKa and pH. It's rather straightforward then.
15. how do we know pka
16. (Original post by nihar97)
how do we know pka
That's the easy bit. Come on...
17. OMG, gold and its decimal places is annoying.
18. (Original post by Ferrarifan 27)
Yeah, I've been having the same problem, how can we find out what diameter it is?
I keep reading figures of around 1 nm to 1.2 nm, but plugging those in gives me stupid answers.
19. (Original post by Snakefingers13)
I keep reading figures of around 1 nm to 1.2 nm, but plugging those in gives me stupid answers.
Wiki says "Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1" but that doesn't give the answer either..?
20. There must be some simpler method for Rg

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