For The III remote Olympiad of Russia on chemistry for the schoolchildren
1. Sulphur is often formed on the slopes of active volcanos during eruption and elaboration of different gazes and vapors. What chemical reactions may lead to sulphur formation?
2. The ground-state electron configuration for copper, silver and gold are 3d104s1; 4d105s1; 5d106s1 respectively. Why do copper and gold in contrast to silver have yellow color?
3. Thermal decomposition of substance A in the absence of a catalyst generates 44,8 l of a gas with density of 1.25 g/l (S.T.P.) and 36 ml of water. Decomposition of substance B also gives 44,8 l (S.T.P.) of a gas, having the same density although a volume of water obtained is two times more. Identify the substances A and B.
4. If 200 g of aqueous solution of carbonate of sodium is added to 200 g of aqueous solution of hydrogen sulfate of sodium a mass of the solution obtained is equal to 395,6 g. If the same solutions are mixed in the reverse order under the same conditions the mass of the final solution is 397,8 g. Calculate mass fraction of the salts in the initial solutions.
5. The decomposition of 1 mole of sulfate of divalent metal yields X g of oxide MeO. In the thermal decomposition of X g of the same sulfate, Y g of oxide MeO is formed. In the thermal decomposition of Y g of the same sulfate, 20 g of oxide MeO is formed. Sulfate of what metal is formed? What is the practical application of this metal and its compound in technology?
6. What organic acids don’t form anhydrides? Give examples of such acids and describe their particular properties.
7. From what organic substance may paranitrochlorbenzene be produced as a result of successive reactions of dehydration, cyclization and two reactions of substitution? Don’t use other organic substances in the transformations .
8. There is magnesium, water and lime-stone in a laboratory. Suggest a scheme of synthesis of phenol. Any installation and catalysts are at your disposal.
gives the reaction of silver mirror. Explain why this reaction proceeds.
10. 2,2,2-trifluoroethanol reacts with diazomethane in heptane as a solvent
but does not react in diethyl ether.
Explain this experimental fact.
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3. Solving the problems should follow a particular strict order with the indication of the number of the problem. You shouldn't rewrite the text of the task.
4. The volume of the answer to each question is not limited, but the brief answers are preferable.
5. If any problem has not been solved, in blanket order of the answers its number and the text "No answer" should be put.
6. Each task is estimated as 10 points maximum. The maximal estimate is 100 points.
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WE WISH YOU SUCCESS!