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28 june, 2015
KProblem 33 question 5B, rate of oxidation is rate = k1*K1*K2*[NF]*[OH-]*[MnO4-] Why there shoul be denominator as stated in answers.
My answer is supporpred by http//vallance.chem.ox.ac.uk/pdfs/KineticsLectureNotes.pdf (page 15-16)
My answer is supporpred by http//vallance.chem.ox.ac.uk/pdfs/KineticsLectureNotes.pdf (page 15-16)
20 july, 2015SCYour expression is correct if we use the current concentrations. But the authors of the problem used the initial concentration of permanganate. Unfortunately, this was not clear from the solution. We made the correction and gave the reference to the original paper.
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27 june, 2015
RFWhy in the solution of the fist problem W for isothermal reversible compression is nRT ln P2/ P1 . Why is not nRT ln P1/P2
28 june, 2015SCBecause work is done on the system. You can use any sign of work - it depends on convention (see comment on p.5 of prep problems)
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27 june, 2015
KelvinIn the solution of the first problem is written W=P(v1-v) and the result is 3500J. If we calculate the result should be negative -3500J.
2 july, 2015SCIt depends on the convention used for the sign of work. Aanyway, the work 3500 J is done ON the gas.
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27 june, 2015
KelvinDear science comiteee
Can I uste the equation dU=Q+W ?
Can I uste the equation dU=Q+W ?
28 june, 2015SCYes - see see comment on p.5 of prep problems.
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27 june, 2015
Devr MadochProblem 8 Why the answer can not be AC(carbon) 4 CTi(titanium)4 BH(hydrogen)1
28 june, 2015SCIt is close, but not exact. If we use integer molar masses, then mass fraction of H in TiH4 is 7.7%, not 7.8%. If, instead, we use exact masses, the it's OK with TiH4 but mass fraction of C in CH4 is 74.9%, not 75%. But, personally, I would accept your solution.
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24 june, 2015
Devr MadochProblem 16 3.1 d Wy we have multiplied 7.5 ml by 2.6 (isnt the titre is 3.3 or 3.5?
24 june, 2015SCIn the corrected version (that of June 15) we multiply by 3.3
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20 june, 2015
KFRI have a question about KF titre. Isn't the KF titre ((16) exercise 3.1) calculated wrong because water and iodine are in ratio 21?
2 july, 2015SCNo, the correct ratio is 1:1
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20 june, 2015
DaveDear Science Commitee
Is there any literature and reference for Problem 4 and 6?
Regards
Dave
Is there any literature and reference for Problem 4 and 6?
Regards
Dave
26 june, 2015JasonWith all due respect, would please gave us the name of the paper instead? Thank you, appriciate your anticipation.
22 june, 2015TimsDear science comitee,
I have problem accessing all the journals of problem 4. Can you give me a direct link to the journal? Because i'll have to pay before i can access the papers thanks.
Tims
I have problem accessing all the journals of problem 4. Can you give me a direct link to the journal? Because i'll have to pay before i can access the papers thanks.
Tims
20 june, 2015SCDear Dave,
both problems are based on original papers.
For problem
4 : The quasi-equilibrium model was
first described in
Batty, G.
Stickney, R., J. Chem. Phys. 52, 4475 (1969).
See also: Nordine, P., J. Electrochem. Sos., 125, 498 (1978) and
Korobov M.,
Bondarenko A.A., Sidorov L.N., Nikulin V. High Temperature Science, 16,
411-420 (1983).
For problem
6: See:
WEILIN XU, JASON S. KONG, YUN-TING E. YEH AND PENG CHEN, Nature Materials
VOL 7 DECEMBER 2008, p. 992 and Supporting
Information for this paper available on line .
Please,
keep in mind that ideas, not numbers, were taken from the original papers.
If you’ll
have problems with reaching of these papers, please, let us know.
both problems are based on original papers.
For problem
4 : The quasi-equilibrium model was
first described in
Batty, G.
Stickney, R., J. Chem. Phys. 52, 4475 (1969).
See also: Nordine, P., J. Electrochem. Sos., 125, 498 (1978) and
Korobov M.,
Bondarenko A.A., Sidorov L.N., Nikulin V. High Temperature Science, 16,
411-420 (1983).
For problem
6: See:
WEILIN XU, JASON S. KONG, YUN-TING E. YEH AND PENG CHEN, Nature Materials
VOL 7 DECEMBER 2008, p. 992 and Supporting
Information for this paper available on line .
Please,
keep in mind that ideas, not numbers, were taken from the original papers.
If you’ll
have problems with reaching of these papers, please, let us know.
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19 june, 2015
Huseyn BabayevHow can we oxidize ketone treatment by Tollens' reagent?
(Problem 25 , compound A3)
(Problem 25 , compound A3)
20 june, 2015SCWith account for decarboxylation, C3H2O3 + 3[O] = CO2 + H2C2O4 (which is equivalent to loss of 6 electrons)
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19 june, 2015
Hien NguyenDear Science Commitee
I have troubles with problem 30 - Synthesis of 3-(4-methylbenzoyl)propyonic acid by Friedel-Craft acylation of Toluene with succinic anhydride. After work up and partial removal of solvents (to about 20%), hexane was added, but there was no precipitate of the desired acid. We have tried several times, with changes of time, temperature and chemicals, but there was no improvement. Could you please tell what should be most concerned for the success of the reaction.
Many thanks.
Hien Nguyen
I have troubles with problem 30 - Synthesis of 3-(4-methylbenzoyl)propyonic acid by Friedel-Craft acylation of Toluene with succinic anhydride. After work up and partial removal of solvents (to about 20%), hexane was added, but there was no precipitate of the desired acid. We have tried several times, with changes of time, temperature and chemicals, but there was no improvement. Could you please tell what should be most concerned for the success of the reaction.
Many thanks.
Hien Nguyen
23 june, 2015Alexander GladilinThe diifficulties may occue from the grade of the reagens. The task authors suggest you doing re-crystallization of the anhydride, drying and further distilling of toluene, and, finally, evaporating the solvent down to 60% before adding hexane. Good luck!
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19 june, 2015
Abdullah HemburkerHello, in the solutions at Problem 16, it is said that hydrazine can be used instead of pyridine for the titration but doesn't it react with iodine according to the reaction
N2H4+ 2I2 ----->N2 + 4HI ?
N2H4+ 2I2 ----->N2 + 4HI ?
5 july, 2015Abdullah HemburkerYes, thank you very much.
2 july, 2015SCHydrazine should not be used instead of pyrydine. However, the negative influence of hydrazine during the water determination can be prevented by using glacial acetic acid instead of methanol
2 july, 2015SCYes, you right. This is a mistake - the idea was to stress the basic character, but we did not take into account redox properties.
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15 june, 2015
KimProblem 24. When we predict the structure of A1 could we choose directly thymidine without mentioning about methyluridine (it is not the major component of nucleic acid - about majority discusses in question)
16 june, 2015SCYes, you may. But still, the majority could be disputable, while the mathematical approach gives clear result.
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13 june, 2015
KimProblem 19. Hello!
On the last step, when obtaining nigricanin from K, does H2, Pd/C remove the MOM protecting group? Is not the MOM protecting group is stable for H2, Pd/C (which removes only benzylic p.g)?
Thanks.
On the last step, when obtaining nigricanin from K, does H2, Pd/C remove the MOM protecting group? Is not the MOM protecting group is stable for H2, Pd/C (which removes only benzylic p.g)?
Thanks.
14 june, 2015SCIndeed, answer contains misprint. MOM group was removed at the previous step (under acidic treatment). So, structure of K should contain OH group instead of OMOM. Tautomeric form can be also written here (ring-chain tautomerism), Both tautomers are right answer..
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12 june, 2015
kPrevious comment was wrong my me (in Karl Fisher reaction, not Bunsen reaction) , but it is still not clearly statet taht one mole of iodine reacts wit one mole of water in Karl Fisher reaction (no realtion with SO2 ir required for calculation of titre), buet titre is correct.
One more question problem 17 3.1.d) what is number 2.6 in answers as titre is 3.3 mg/L and correction is 2.8 mg of water for whole sample.
One more question problem 17 3.1.d) what is number 2.6 in answers as titre is 3.3 mg/L and correction is 2.8 mg of water for whole sample.
15 june, 2015SCA ratio between reagents is clearly stated in the reaction equation.There is a mispint in the answer. Titre 3,3 mg/ml should be used for calculations.
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12 june, 2015
KProblem 17 citation from answers One molecule of iodine
reacts with one molecule of sulphur oxide, so the
theoretical titre is (in mg/mL) ... but 1 mol iodine reacts with 2 mol of water (reaction I2 + SO2 + 2H2O --> 2HI + H2SO4) and titree is titre = 0.193*2*18/1000 = 6.94 mg/mL
reacts with one molecule of sulphur oxide, so the
theoretical titre is (in mg/mL) ... but 1 mol iodine reacts with 2 mol of water (reaction I2 + SO2 + 2H2O --> 2HI + H2SO4) and titree is titre = 0.193*2*18/1000 = 6.94 mg/mL
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10 june, 2015
itaiHello,
Regarding to the use of Excel - I noticed that you didn't note in which version of Excel (2003/2007/2010/2013...) we are expected to know the required skills. It would be very helpful if you will note which version will be used in the olympiad.
Thanks )
Regarding to the use of Excel - I noticed that you didn't note in which version of Excel (2003/2007/2010/2013...) we are expected to know the required skills. It would be very helpful if you will note which version will be used in the olympiad.
Thanks )
12 june, 2015SCThe versions of the software we propose are Windows 8 and Excel 2013.
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4 june, 2015
LimHi, in the solutions published, for problem 18, two possible structures for compound I are proposed, one of which is later rejected. Shouldn't one of the compound proposed be 1,2-dimethylcycloocta-1,5-diene instead of 1,6-dimethylcycloocta-1,5-diene?
10 june, 2015SCYes, 1,2-dimethylcycloocta-1,5-diene should be considered as one of possible alternatives. It is my fault.
9 june, 2015LimYes, but 1,2-dimethylcycloocta-1,5-diene isn't even proposed in the first place before being rejected. It is mentioned that only 1 product is furnished upon oxidative or reductive treatment. If the compound proposed by the authors, 1,6-dimethylcycloocta-1,5-diene is possible (before we reject it for not having a centre of symmetry) , then two products should be available upon ozonolysis.
8 june, 2015SCCompound I must have center of symmetry, while 1,2-dimethylcycloocta-1,5-diene has not
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21 may, 2015
Oguz KilimangereaHello, regarding problem 28, the precipitate of lead oxalate did not dissolve even with 90 mL of boiling hot 0,5 M nitric acid.Do you recommand to use the reagent( 1 M sulphuric acid) from the original procedure?( There were more people in our country who tried with nitric acid and it did not dissolve either).
27 may, 2015Alexander GladilinIn the Protocol it is said that the precipitate is to be dissolved directly on the filter. You were not supposed to boil it with HNO3. The trick is that the reaction is reversible and you have to remove the excess of nitric acid for complete dissolution. This is achieved if the filter with the precipitate is treated with the acid ("flow-through" mode).Ч
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21 may, 2015
Kychytky (potential participant)How can I prepare for IChO 47. I dont know what to study
21 may, 2015SCJust solve the Preparatory Problems
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18 may, 2015
MenWhen will the solutions of preparatory problems be publishet?
19 may, 2015SCThe answers and solutions was sent to head mentors by February 15, on this site they will be posted by May 31
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