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#### Rutherford

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« on: February 04, 2013, 10:57:52 AM »
Okay, the preparatory problems are on this page http://icho2013.chem.msu.ru/materials/Preparatory_problems_IChO_2013.pdf. Whoever wants may post his attempt on a problem, so we can all together check our solutions. I will start with the first and half of the second problem:

1st Problem
:
1. Pros:
-bigger distance between the layers, so they can be easier separated;
-the carbon atoms attached to oxygens are more reactive that the regular atoms in graphite and they can easier undergo reactions during the synthesis of graphene.
Cons:
-you have to remove oxygen.
2. x=0.375, xmax=0.5;
3. -OH, -COOH, -C=C-, -C-O-C-;
4. I got 34%, but I don't understand the part with upper and lower limit;
5. CH0.22O0.46*0.67H2O.

2nd Problem:
1. ΔH=-467.5 kJ/mol, ΔG=-454.5 kJ/mol, Nγ=2.59;
2. ΔG=-438.3kJ/mol;
3. 25.9%

Anyone got somewhere a similar result? If not, where is the difference?
« Last Edit: February 04, 2013, 11:18:54 AM by Raderford »

#### AWK

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« Reply #1 on: February 04, 2013, 11:30:46 AM »
Quote
5. CH0.22O0.46*0.67H2O.
Each water is joined through hydrogen atoms with two oxygens. What is maximum amount of water per atom of carbon?

Concerning 3.
In my opinion name graphene oxide include double bonds.
http://bucky-central.me.utexas.edu/RuoffsPDFs/211
On the base of above work I would rather use secondary and tertiary OH groups as different functional groups.
« Last Edit: February 04, 2013, 11:50:48 AM by AWK »
AWK

#### Rutherford

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« Reply #2 on: February 04, 2013, 12:09:56 PM »
AWK, thanks very much for the reply.
The oxygens are from different sheets of GO, so per 1 carbon atom, there are 0.22 -OH groups which bond to 0.22 H2O molecules and 0.24 -O- groups which bond to 0.24 water molecules, is it 0.22+0.24=0.46 then?

3. -OH group is a functionally group. I am not sure how could I represent secondary and tertiary alcohols as they contain the same group, which is -OH.

#### AWK

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« Reply #3 on: February 05, 2013, 08:43:28 AM »
AWK, thanks very much for the reply.
The oxygens are from different sheets of GO, so per 1 carbon atom, there are 0.22 -OH groups which bond to 0.22 H2O molecules and 0.24 -O- groups which bond to 0.24 water molecules, is it 0.22+0.24=0.46 then?

3. -OH group is a functionally group. I am not sure how could I represent secondary and tertiary alcohols as they contain the same group, which is -OH.
It does not matter that oxygen atoms  come from different sheets - just look on stoichiometric unit of GO.
3. This is a question what authors meant.
AWK

#### Rutherford

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« Reply #4 on: February 05, 2013, 08:51:49 AM »
I think I understood, is it 0.23 then?

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« Reply #5 on: February 12, 2013, 03:59:45 PM »
Has anyone done Problem 14? I'm not really sure where to start (partly because I'm unclear on the definition of "standard biochemical redox potential" as opposed to "standard potential").

#### Rutherford

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« Reply #6 on: February 15, 2013, 05:07:42 AM »
No idea. If someone knows it would be nice to share here.

#### Borek

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« Reply #7 on: February 15, 2013, 05:30:31 AM »
Has anyone done Problem 14? I'm not really sure where to start (partly because I'm unclear on the definition of "standard biochemical redox potential" as opposed to "standard potential").

My understanding is that it is just converted to pH 7.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

#### UG

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« Reply #8 on: February 15, 2013, 05:36:36 AM »
Are you going to the competition Raderford?

#### Rutherford

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« Reply #9 on: February 15, 2013, 07:12:58 AM »
I didn't even went to the National Olympiad this year, yet, but this seems like lot fun to me, so I want to attempt these preparatory problems. If I pass then good, if not, at least I learned many new things.

Something changed with the 1st problem.
« Last Edit: February 15, 2013, 07:23:03 AM by Raderford »

#### Rutherford

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« Reply #10 on: February 16, 2013, 08:41:57 AM »
Anyone determined the unknown tin compound in the 4th problem?

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« Reply #11 on: March 04, 2013, 12:57:40 PM »
Does anyone have any books they would recommend to build your level of chemical knowledge up for an exam like this? I have mostly been browsing the Internet till now, I was wondering if someone who's seen a couple of past papers could make a good guess and some suggestions for what books to read to build up my knowledge of chemistry more thoroughly up to this level.

Edit: They tend to question only a few topics each year but I would be very grateful for a textbook that covers all of them in that much detail

#### Sophia7X

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« Reply #12 on: May 02, 2013, 12:58:54 PM »
Raderford did you finish this problem set yet?
Entropy happens.

#### Rutherford

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« Reply #13 on: May 03, 2013, 04:26:37 AM »
Nope. I can't find the problems anymore  .

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