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5 mart, 2015
WesIn problem 29 procedure C ,when we add PAN into the solution, we get yellow but not pink, why?
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5 mart, 2015
KetimHi, in problem 24, when the text says D and nucleoside N differs by one atom only, that means that
- D has one atom more/less.
- D has one atom more of another element (but the same number of atoms as N)
Thank you!
- D has one atom more/less.
- D has one atom more of another element (but the same number of atoms as N)
Thank you!
6 mart, 2015SCD has one atom more/less
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4 mart, 2015
KelliIn Problem 28, is it feasible to determine the amount of lead in the alloy using permanganate? It is possible to precipitate the lead as lead oxalate. Howver, dissolving the lead oxalate in sulfuric acid will not occur as lead sulfate precipitate will occur. If you dissolve the lead oxalate in other acids, such as HCl or nitric acid, the anions will interfer with the permanganate titration. Please advise.
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3 mart, 2015
AndriyHi, I have a questions about problem 26. Would Ag2O precipitate when we add supernatant (where is the excess of Ca(OH)2) to the excess of AgNO3?
6 mart, 2015SCIt's not impossible, but Ag2O was not taken into consideration
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3 mart, 2015
Abdullah HemburkerHello, I wanted to ask if, at Problem 9, the copper chloride we are supposed to synthesise has to be anhydrous or hydrated.
3 mart, 2015SCAnhydrous
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2 mart, 2015
PortaHi, in problem 25, question 2; the mass of precipitated Ag is correct? Because I think that it has to be 0.752g, so the estructure of A3 makes sense (the amount of -CHO groups in it). Thank you.
24 mart, 2015SCReally 7.52g.
23 mart, 2015PortaHi, can you please tell me if I was right? Or the mass of Ag is really 7.52g. Thank you!
3 mart, 2015V RaicevicDisregard my comment, I thought you were commenting on problem 22. Sorry.
3 mart, 2015V RaicevicThe problem is correct and a very good one at that! Please see my previous comments, they will give you the necessary insight.
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1 mart, 2015
Steven SmithIn the problem 2.3, what is the pressure in the container during the transportation of methane?
3 mart, 2015Steven SmithI have once again gone through the problem and have realized my misunderstanding. No more queries now and yeah a very interesting problem. Thanks!
3 mart, 2015Steven SmithBut during transportation, methane is in liquid form so how can we find it's saturated pressure?
2 mart, 2015SCThe saturated pressure of methane
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1 mart, 2015
Steven SmithIn the last part of Problem 5, what does r stand for?
2 mart, 2015Steven SmithThanks!
1 mart, 2015SCActually, r is r(obs), the observed rate
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28 fevral, 2015
StephanI am not entirely sure what kind of work is asked for in problem 1, questions 1 and 2. Is this work, that is supplied to the system only in the adiabatic process, or should we also take into the account the work that is involved in isobaric cooling or heating?
1 mart, 2015SCBoth
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28 fevral, 2015
Maurice Cosandey, Swiss delegationWhat is the unit of the flow rho, in 4.2.4 ?
28 fevral, 2015SCFlow unit is the same as rate unit, dn/dt (pressure and square root of mass are incorporated into the constant c)
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27 fevral, 2015
KetimHello, would you please tell me if in Problem 17, the molecular formulae of L(C14H24O6) is correct? Because I think that there are more oxygens in the compound L...
Best regards.
Best regards.
2 mart, 2015KetimI think that I have found it, and it has that formulae. Thank you.
28 fevral, 2015SCL is really C14H24O6. If you have serious reasons against it write, please, to the Organising Committee
28 fevral, 2015CuriousSo strange... How about number of hydrogens?
27 fevral, 2015SC6 oxygens in L is correct
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23 fevral, 2015
I. DimitrovaWould you pleace tell me in Problem 1, 5th question, is the value of the efficiency eta=0.379 correct? I think it should be 0.319.
26 fevral, 2015SCIt is correct. If you believe, it is wrong, please, support your opinion with the arguments and send the letter to the organizers.
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22 fevral, 2015
adamhi.
i have a question about the first problem in the first 2 questions do we consider the process cooling first then compressing or the compression first.
and if any one could help me with the difference in calculation between max and min work.
i have a question about the first problem in the first 2 questions do we consider the process cooling first then compressing or the compression first.
and if any one could help me with the difference in calculation between max and min work.
26 fevral, 2015SCSorry, team leaders asked not to discuss solutions before May, 31
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19 fevral, 2015
JJFor Prob 18, Qn2 is there any mistake with Product F?
26 fevral, 2015SCYou are right, Swern oxidation of alcohol is not selective, so -CH2OH group in F should be replaced by -OCH3
25 fevral, 2015JJsorry, I meant product F of problem 17.
20 fevral, 2015SCNo.
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18 fevral, 2015
Vladimir VitSorry,
I counted wrong(no hydrolysis acetyl salicylic acid).
Thank You.
Vladimír Vít
I counted wrong(no hydrolysis acetyl salicylic acid).
Thank You.
Vladimír Vít
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17 fevral, 2015
Vladimir VitPlease,
are You sure in Problem 14, that mass of powdered Aspirin is correct? I think mass of Aspirin is too large. To titration go 1/10 of 4.4035 g(i.e. 0.44035 g), n(bromine)=3 n(bromate) ; in 100 mL is 0.001 mol bromate, in 20 mL 0.0002 mol. It is 0.0006 mol bromine total to titration. Resting bromine is retitrated by As(III). Moles of Aspirin are from 0.00265(total acetylsalicylic acid)to lover moles(salicylic acid is resting mass). I think mass of Aspirin powder may be 1/20 th of declared mass(i.e about 0.2215 g to dissolving on250 mL).
Thank You.
Vladimir Vit
are You sure in Problem 14, that mass of powdered Aspirin is correct? I think mass of Aspirin is too large. To titration go 1/10 of 4.4035 g(i.e. 0.44035 g), n(bromine)=3 n(bromate) ; in 100 mL is 0.001 mol bromate, in 20 mL 0.0002 mol. It is 0.0006 mol bromine total to titration. Resting bromine is retitrated by As(III). Moles of Aspirin are from 0.00265(total acetylsalicylic acid)to lover moles(salicylic acid is resting mass). I think mass of Aspirin powder may be 1/20 th of declared mass(i.e about 0.2215 g to dissolving on250 mL).
Thank You.
Vladimir Vit
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16 fevral, 2015
Maurice Cosandey, Swiss delegationProblem 2.1. Is the value 16 800 tons of liquid methane correct ?
Liquid methane has a density of 420 kg/m3. So a tank of 40000 m3 weighs 18 600 tons, and not 16 800 tons.
Liquid methane has a density of 420 kg/m3. So a tank of 40000 m3 weighs 18 600 tons, and not 16 800 tons.
16 fevral, 2015SC0.420 ton/m3 * 40000 m3 = 16800 ton
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16 fevral, 2015
Maurice Cosandey, Swiss delegationOn February 13, you published a correction for Problem 11, namely "Bromate" was replaced by "Bromine", This has nothing to do with Problem 11, but it concerns Problem 14.
16 fevral, 2015SCCorrected, thank you
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15 fevral, 2015
V RaicevicDisregard my previous comment, I forgot that the stoichiometry of formaldehyde being oxidized in the Tollens' reaction is 14. Quite good problem!
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15 fevral, 2015
V RaicevicI have to make a further comment. After solving the problem (I am not going to go through the details), I believe the mass of the first sample of X is off by a factor of 2, i.e. it should be 0.216 g rather than 0.108 g. This is because 0.432 g of metallic silver is equivalent to 0.004 mol, meaning the quantity of the aldehyde should be 0.002 mol (Tollens stoichiometry 12), and since Xaldehyde stoichiometry in the hydrolysis reaction is 11, this should also be the quantity of the first sample of X. However, from the precipitate masses and functional group identification I've found the molar mass of compound X to be 108 g/mol, and not 54 g/mol as the mass of silver implies.
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