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14 february, 2015
V RaicevicDear Science Committee, I have a question regarding Problem 22, or more particularly, about the part with precipitates. I find the pair of sentences "Another part was passed through NaOH solution. After some time the excess of BaCl2 solution was added." somewhat ambiguous. My first concern is about the identity of the solution to which BaCl2 is added. If the gas is passed through a solution by means similar to Drechsel's bottle, this means all of the CO2 is eliminated (dissolved as Na2CO3 and/or NaHCO3). I am guessing that the rest of the gas is then dissolved in another solution, and NaOH is added subsequently. If this is not the case, i.e. if BaCl2 is added to the solution which now contains Na2CO3 and/or NaHCO3, we are prevented from doing any calculations and deductions because the quantity of NaOH was not specified. If this is the case, there is still the problem of the higher mass of the precipitate. How can we obtain more precipitate if we remove CO2 which is certainly formed in substantial quantities after burning X? I see no third possibility, yet I might be mistaken. I would appreciate your answer. P.S. The problems are really intriguing, it is very enjoying to solve them. Great job.
15 february, 2015V RaicevicThank you for your replies.
15 february, 2015SCYes, it is possible, if NaOH is in a large excess. But in this case, the problem can not be solved. So, let us believe that NaOH is in the stoichiometric amount to form carbonate and sulfite. (Moreover, in an open air, the solution can absorb additional CO2 from the atmosphere but we ignore this possibility)
15 february, 2015V RaicevicHowever, I still feel that if it is as you state that NaOH is in excess,
the possibility of Ba(OH)2 precipitating out to a degree (after the
addition of BaCl2) is not ruled out.
the possibility of Ba(OH)2 precipitating out to a degree (after the
addition of BaCl2) is not ruled out.
15 february, 2015V RaicevicThank you for the insight.
15 february, 2015SCThe idea is very simple. In both cases we meant the excess of OH-, CO2 and SO2 are absorbed completely, and in the second case sulfite is oxidized on air.
15 february, 2015Peng L.Y.air(after some time)
15 february, 2015V RaicevicI meant to say "and BaCl2 is added subsequently."
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13 february, 2015
Kees BeersIn problem 14 am I right that the line 'Redox titration using bromate as an oxidation agent is one of the possible techniques to determine acetylsalicylic acid in aspirin.' should better be 'Redox titration using bromine as an oxidation agent is one of the possible techniques to determine salicylic acid in aspirin.'?
15 february, 2015SCYes, you are right. Of course, we cannot determine acetylsalicylic acid with bromine. Correction was made.
15 february, 2015Kees BeersYou did not fully correct the tekst: it still says '... to determine acetylsalicylic acid...' where I proposed '... to determine salicylic acid...' Moreover I think that 'Reaction using bromine ..' is even better than 'Titration with bromine...' .
14 february, 2015SCYes, the text was corrected, thank you.
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12 february, 2015
Cui J.M.In Problem 11, to calculate the mass fraction of iron exactly(34.9%), which atomic mass data should I use?
Fe 55.85 C 12.01 H 1.008 N 14.01 O 16.00
or Fe 56 C 12 H 1 N 14 O 16 ?
Thank you!
Fe 55.85 C 12.01 H 1.008 N 14.01 O 16.00
or Fe 56 C 12 H 1 N 14 O 16 ?
Thank you!
14 february, 2015Science CommitteeThe correct value is: w(Fe) = 34.9% !
14 february, 2015M.P.agree with mr. Peng
13 february, 2015Science CommitteeNo misprint. You may use 55.8 for Fe, other atomic masses integer
13 february, 2015Cui J.M.And I wonder if there is a misprint about the mass fraction?
13 february, 2015Peng L.Y.I think it should be 45.5% , not 34.9%.
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12 february, 2015
Y In problem 7 solvent is ethanol or water ?
14 february, 2015SCRead the problem thoroughly - no solvent! ALL substances except catalyzer are in the expressions for equilibrium constants.
14 february, 2015Namewhat does it mean. when you say water enters both constants? That we shouldn't put it un equation, or should? and should we enter the ethanol in the equstion if it is solvent?
13 february, 2015Science CommitteeEthanol, so water enters both constants
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12 february, 2015
Yasuyuki Egashira ( Tokyo University of Technology )I have some question on the Problem 33
1) 1st paragraph, 2nd line
I suppose "fluoroquinoline" is miss-spelling of "fluoroquinolone".
2) In paragraph under the "D. Questions and Data Analysis, 4. "
"The mechanism or Norfloxicin oxidation..."
must be
"... mechanism of ...".
1) 1st paragraph, 2nd line
I suppose "fluoroquinoline" is miss-spelling of "fluoroquinolone".
2) In paragraph under the "D. Questions and Data Analysis, 4. "
"The mechanism or Norfloxicin oxidation..."
must be
"... mechanism of ...".
13 february, 2015Science CommitteeYou are right, thank you. Both were corrected.
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9 february, 2015
Carlos Cerqueira (Brazilian Instructor)Problem 25.2
I would like to confirm with scientific committee if the mass of A3 is really 1.00 g.
I think that the correct value should be 10.0g. Thanks
I would like to confirm with scientific committee if the mass of A3 is really 1.00 g.
I think that the correct value should be 10.0g. Thanks
9 february, 2015Science CommitteeReally 1.00 g.
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8 february, 2015
K. BenovaProblem 26 It appears to me that there is a contradiction in the data concerning compound Z. Data about the gas refers to hydrogen chloride, but the remaining data shows that Z is fluoroacetic acid, e.g. it does not contain chlorine.
10 february, 2015K. BenovaWonderful task, thank you!
9 february, 2015Science CommitteeNo contradiction. Consider, e.g., acetic acid. It is an individual compound, but in gas phase it is a mixture of dimers and monomers.
9 february, 2015К. Benova""ONE of the gaseous products of Z combustion has the density of 1.43 g/L (measured at 34C,
750 Torr);"" ONE OF ???
750 Torr);"" ONE OF ???
9 february, 2015Science CommitteeNo contradiction. 36.5 g/mol is not only HCl, it can correspond to a mixture of gases
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7 february, 2015
Abdullah HemburkerExcuse me for bothering you, but at Problem 2, question 5, is the information about the time(9 months) and the heat flux really neccesary? If so, how many days should a month be considered to have? Thank you.
16 february, 2015aasmai've calculated problem 1 ,but the value of minimum work is greater than the value of maximum work,first i calculated final temperature.tby using reversible adiabatic equation.
9 february, 2015Science CommitteeYes, it is necessary. Take the average month as 30.5 days
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7 february, 2015
John ChiPlease tell me where are the keys of the preparatory problems?
8 february, 2015Science CommitteeThe solutions will be sent to head mentors only. They will be in an open access only at May, 31
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7 february, 2015
AlexIn the second problem, question 4, is it true that the total heat leakage is 50 kW, because for 15 days, that's a lot of heat, and in my calculations, that can vaporize more CH4 than there actually is. And in question number 3, should we account the change in volume for enthalpy?
10 february, 2015AlexThank you for the answer. I found the mistake.
9 february, 2015Science CommitteeYour calculation is wrong, check the units
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7 february, 2015
Cui J.M.In Problem 12.2 and 12.3, does the complex react with one equivalent of thiourea or more? Thank you.
8 february, 2015Science CommitteeThe excess of thiourea is used.
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7 february, 2015
XIn P25.3, while determining B2, I found that all I can derive from B1 and the text contradicts with "B2 reveals 4 signals in 13C-NMR spectrum". Possible "B2"s could only reveal 5 or 7 signals. Is this a typo or something?
15 june, 2015KimProblem 25. In the text I have downloaded, there is not written any type of NMR (... B2 reveals 4 signals in.(?) B2 and ...)
and
in the corrections - it corrected vise versa
and
in the corrections - it corrected vise versa
9 february, 2015Science CommitteeYes, you are right, it was a typo. B2 reveals 4 signals in 1H-NMR spectrum. We made a correction in the text. Thank you.
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6 february, 2015
Mustafa RakliuFor problem 24, can you please tell me if the mass percent of P and O are correct? I think there might be an error.
6 february, 2015Sciece CommitteeYes, the mass content of P and O is absolutely correct.
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5 february, 2015
Cui J.M.There is a description in Problem 26, which is "It is known that molecules of Y and X differ by one element, Y having one atom more. " Does it mean the kinds of elements of Y and X are the same, and only the number of one kind of atoms differs? Or does it means the kinds of elements of Y and X are different, and the total number of atoms of Y is more? Or does it have other meaning? Could you please tell me? Thank you!
6 february, 2015Science Committee1) The total number of atoms in Y exceeds the total number of atoms in X by 1. 2) X and Y differ by one element only (as, say, NO and CO2)
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5 february, 2015
Kabylda AdilIn Problem 21, is K really a product of [2+2] cylcoaddition ?
6 february, 2015Science CommitteeYes, definitely
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4 february, 2015
QIn N22. What compound is A?
5 february, 2015Peng L.Y.I think A is CH2O.
4 february, 2015Science CommitteeNo hints before May, 31. Sorry
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4 february, 2015
Peng L.Y.I have another question that, in problem 8,it might be 'The mass fraction of A in the compound with B is75%,and the mass fraction of A in the compound with C is 7.8%' Because I find an answer accord with it.
5 february, 2015Peng L.Y.Yes, this problem is right，after thinking twice with the problem.
5 february, 2015Science CommitteeThis answer is wrong. And the text of the problem is correct.
5 february, 2015Peng L. Y.In another saying,that 'the mass fraction of B in the compound with A is 75%',I think the three elements are C,Cl,H .And ω（C）in CCl4 is 7.8%,ω（C）in CH4 is 75%.
4 february, 2015Science CommitteeNo, the mass fraction of B in the compound with C is 7.8%. The text is correct.
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4 february, 2015
Peng L.Y.Problem 28,Procedure A,Decomposition of the alloy sample, 'If still so,add a minimal amount of HCl to dissolve the residue' But I think that we should use HNO3 instead of HCl.Because both PbCl2 and AgCl are precipitates.
4 february, 2015Science CommitteeSure, it is a misprint. Sorry. We made a correction in the text
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4 february, 2015
MacedonianChemistHello , I am a potential participant from FYR Macedonia. Can you tell me more about individual application for ICho ?
4 february, 2015IChO 2015To participate in IChO you must: 1) win the national olympiad, 2) qualify to the national team of four students in your country.
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5 february, 2015
NamikI don't understand, this ICHO is held by Russians, only in Baku, Azerbaijan? Where are Azerbaijani teachers, professors? Thank you in advance for possible answers.
5 february, 2015IChO 2015 IChO 2015 is held by Baku Branch of Lomonosov Moscow State University as it is mentioned in the site. Distinguished chemists, professors and experts in the field of Chemistry of Azerbaijan are members of the Olympiad Organizing Committee and Science Committee. The preparatory problems attached to the site are only samples. Different kinds of problems will be included in the list of preparatory problems worked out by experts from Azerbaijan.
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