Şərhlər

20 iyul, 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. 

28 iyun, 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)

2 iyul, 2015SCIt depends on the convention used for the sign of work. Aanyway, the work 3500 J is done ON the gas.

28 iyun, 2015SCYes - see see comment on p.5 of prep problems.

28 iyun, 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.

24 iyun, 2015SCIn the corrected version (that of June 15) we multiply by 3.3

2 iyul, 2015SCNo, the correct ratio is 1:1

26 iyun, 2015JasonWith all due respect, would please gave us the name of the paper instead? Thank you, appriciate your anticipation.

22 iyun, 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

20 iyun, 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.

20 iyun, 2015SCWith account for decarboxylation, C3H2O3 + 3[O] = CO2 + H2C2O4 (which is equivalent to loss of 6 electrons)

23 iyun, 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!

5 iyul, 2015Abdullah HemburkerYes, thank you very much.

2 iyul, 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 iyul, 2015SCYes, you right. This is a mistake - the idea was to stress the basic character, but we did not take into account redox properties. 

16 iyun, 2015SCYes, you may. But still, the majority could be disputable, while the mathematical approach gives clear result.

14 iyun, 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..

15 iyun, 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.

12 iyun, 2015SCThe versions of the software we propose are Windows 8 and Excel 2013.

10 iyun, 2015SCYes, 1,2-dimethylcycloocta-1,5-diene should be considered as one of possible alternatives. It is my fault.

9 iyun, 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 iyun, 2015SCCompound I must have center of symmetry, while 1,2-dimethylcycloocta-1,5-diene has not

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

21 may, 2015SCJust solve the Preparatory Problems

19 may, 2015SCThe answers and solutions was sent to head mentors by February 15, on this site they will be posted by May 31