cm3 and a density of 1.12 g/cm3, formed after the condensation of combustion products, was added to a solution of sodium bicarbonate, which was in excess. as a result, gas was released with a volume of 5.6 dm3(n.c.). calculate the volume (dm3, n.c.) of oxygen that reacted under the conditions of the experiment
its combustion through lime water precipitated 76 g of sediment
1) The homologue of methanol isA) toluene
B) methanal
C) glycerin
D) propanol
2) an ester is formed by the interaction of methane acid with
A) methane
B) ethanol
C) sodium hydroxide
D) sodium carbonate
3) potassium permanganate solution becomes colorless when interacting with
A) benzene
B) ethylene
C) ethanol
D) methane
4) which of the following processes is not a redox process?
A) lime slaking
B) burning natural gas
C) metal corrosion
D) water decomposition
5) Iron(II) chloride can be obtained by interaction:
A) chlorine and iron
B) hydrochloric acid
C) solutions of iron(II) chloride and copper(II) sulfate
D) iron and magnesium chloride solution
6) Why doesn't water burn?
A) water is liquid
b) water is made up of carbon
C) water is a product of the complete combustion of hydrogen
D) water is a product of incomplete combustion
7) Why do small explosions with sparks sometimes occur when a match is lit?
A) a lot of sulfur
B) little oxygen
C) apply crystalline bctoleth salt
D) lots of oxygen
8) Which stone emits combustible gas under the influence of water?
A) marble
B) calcium carbide
C) limestone
D) quartz
9) Has an atomic crystal lattice
A) iron
B) carbon monoxide (IV)
C) silicon oxide (IV)
D) hydrogen
10) Carbon and silicon atoms are similar:
A) the number of protons in the nucleus
B) the number of energy levels
C) the total number of electrons
D) the number of valence electrons
11) Carbon dioxide in the laboratory is obtained:
A) carbon monoxide oxidation
B) glucose fermentation
C) decomposition of malachite
D) the action of acid on marble, chalk or limestone
12) acid oxide is
A) carbon monoxide (II)
B) nitric oxide (I)
C) nitric oxide (V)
E) nitric oxide (II)
13) the largest number of cations is formed with complete dissociation of 1 mol
zinc
A) sodium phosphate
B) aluminum nitrate
C) iron(III) chloride
E) iron(III) sulfate
14) Both sulfur and chlorine react
A) with oxygen
B) with potassium sulfate
C) with iron
D) with oxide
15) at room temperature react
A) sulfur and oxygen
B) nitrogen and oxygen
C) barium and water
D) zinc and water
2. The strongest basic properties are
1) aniline 3) methylamine 2) ammonia 4) dimethylamine
3. Possesses the weakest basic properties
1) ammonia 3) diphenylamine 2) aniline 4) dimethylamine
4. The main properties of amines increase in sequence
1) aniline - dimethylamine - methylamine
2) aniline -- diphenylamine ---- triphenylamine
3) phenylamine---methylamine----dimethylamine
4) triphenylamine - trimethylamine - methylamine
5. Medium aqueous solution of methylamine
1) alkaline 3) acidic 2) neutral 4) slightly acidic
6. In an aqueous solution of dimethylamine, litmus becomes colored
7. In an aqueous solution of methylammonium sulfate, litmus becomes 1) orange 3) blue 1) red 4) purple
8. In an aqueous solution of aniline, litmus has a color
I) crimson 3) blue 2) red 4) purple
9.. Methylamine interacts with 1) NaOH 3) KCL 2) H2SO4 4) H2,
10. Ethylamine interacts with each of the three substances
1) KOH, ZnO. HNO2
2) HI, H „ С6Н5СН3 *
3) Cu(OH)2, HaSO4! CO2
4) H20, HBr, O2
11. Trimethylamine does not interact with
12. Methylamine interacts with each of the two substances
4) Mg(OH)2 and N2
13. ANILINE interacts with
14. ANILINE interact with each of the two substances
1) KOH and H2SO4,
3) CaO and H 2
2) HCI and C6H6
15. Aniline does not interact with
1) barium hydroxide 3) bromine water
2) hydrogen bromide 4) sulfuric acid;
16. The products of complete combustion of amines are
1) carbon dioxide, water and nitric oxide (P)
2) carbon monoxide (P), water and ammonia
3) carbon dioxide, water and nitrogen
4) carbon dioxide, hydrogen and nitrogen
17. And methylamine, aniline interact with each of the two substances
1) bromine water and hydrogen bromide
2) hydrogen and sulfuric acid
3) water and sodium hydroxide
i 4) hydrochloric acid and oxygen
combustion (in excess of oxygen), 10.08 l (n.u.) of a mixture of ethane and propane was passed through an excess of lime water. In this case, 120 g of sediment was formed. Determine the volumetric composition of the initial mixture.
school stage
8th grade
Task 1. TEST(3.5 points)
Choose one correct answer (1 point for each answer)
1. The smallest particle of a substance, which is the carrier of its chemical properties, is called:
1. grain 2. crystal 3. atom 4. molecule
2. Which element is named after a celestial body - a satellite of the Earth:
1. Co - cobalt 2. Te - tellurium
3. Se - selenium 4. U - uranium
3.
One of the first metal alloys that man began to use in ancient times is:
1. steel; 2. bronze; 3. duralumin; 4. cast iron; 5. will win.
4. Pure substances include:
1. vinegar 2. distilled water
3. air 4. milk
5. Is a substance:
1. dew drop; 2. copper coin;
3. a piece of chalk; 4. mercury.
6. Substances have the same relative mass, the formulas of which are:
1. CuSO 4 and CuS 2. CuS and CuO
3. CuO and Cu 2 S 4. CuSO 4 and Cu 2 S
7.Specify a simple substance that is not a metal:
1. tin; 2. phosphorus; 3. mercury; 4. magnesium; 5. copper.
Task 2.(2 points)
At the beginning of the 20th century, geologists encrypted on maps the places of discovery of ores of valuable metals using the coordinates of chemical elements in the Periodic system. The Arabic numeral indicated the number of the period, and the Roman numeral indicated the number of the group. In addition, the records also contained letters of the Russian alphabet - A and B. On one of the old maps of maps, the designations were found: 4VIB, 4VIIIB2, 6IB, 6IIB. Task: Decipher the records of geologists.
Task 3.(6 points)
Suggest several options (no more than three) for solving the chain of reactions A → B → C and make up the reaction equations for this scheme. Substances A, B, C are complex inorganic compounds belonging to different classes of compounds.
Task 4.(3 points)
Who among us has not dreamed of finding treasures hidden once, in the mists of time, by sea pirates?! If you solve the puzzle, you will know how to find the real treasure for sure.
Task 5.(4 points)
So that Cinderella could not go to the ball, her stepmother came up with a job for her: she mixed salt with small nails, wood shavings and river sand and told Cinderella to clean the salt and put the nails in a separate box. Cinderella quickly completed the task and managed to go to the ball. Explain how you can quickly complete the stepmother's task.
Task 6.(6 points)
In nature, iron forms a number of minerals. These are magnetite Fe 3 O 4, hematite Fe 2 O 3 limonite 2Fe 2 O 3 3H 2 O. In which of the minerals is the mass fraction of iron the largest.
All-Russian Olympiad for schoolchildren in chemistry (2016-2017)
school stage
Grade 9
Task 1. TEST(3 points)
Each question has multiple answers, of which only one is correct. Choose the correct answer. Write down the number of the task and put the number of the selected answer.
1. Has the highest molecular weight
1) BaCl 2 2) BaS0 4 3) Ba 3 (P0 4) 2; 4) Ba 3 R 2.
2. The sum of the coefficients in the molecular reaction equation
(CuOH) 2 CO 3 + HC1 \u003d CuC1 2 + CO 2 + ...
1) 10: 2) 11; 3) 12; 4) 9.
3. The amount of substance (mol) contained in 6.255 g of phosphorus (V) chloride
1) 0,5; 2) 0,3; 3) 0,03; 4) 0,15.
4. The number of protons and neutrons in the isotope nucleus 40 To
1) p = 20, n=19; 2) p = 40, n = 19;
3) p=19, n=21: 4) p=21,n=19.
5. Reaction resulting in a precipitate
1) KOH + HC1; 2) K 2 C0 3 + H 2 S0 4;
3) Cu (OH) 2 + HNO 3; 4) Na 2 S + Pb(N0 3) 2 .
6. 150 g of calcium chloride were dissolved in 250 ml of water. The mass fraction of salt in solution (in percent) is:
1) 60; 2) 37,5; 3) 75; 4) 62,5
Task 2.(7 points)
Given a chain of transformations:
X→XO 2 →XO 3 → H 2 XO 4 → K 2 XO 4
K 2 XO 3 KMnO4/H+
Determine the element X. Write the equations for the corresponding reactions.
Task 3.(3 points)
Write the reaction equations by which, using the simple substances calcium, phosphorus and oxygen, calcium phosphate can be obtained.
Task 4.(3 points)
The sum of protons, neutrons and electrons in an atom is 42. The number of neutrons is equal to the number of protons. Define a chemical element. Give explanations.
Task 5.(3 points)
When 9.6 g of metal (III) oxide interact with sulfuric acid, 24 g of metal (III) sulfate is formed. Define metal.
Task 6.(5 points)
Four numbered flasks contain solutions: sodium hydroxide, sodium chloride, hydrochloric acid and phenolphthalein. How to determine which bottle contains which substance without using additional reagents, but having a sufficient number of empty test tubes. Write the equations of the reactions carried out.
All-Russian Olympiad for schoolchildren in chemistry (2016-2017)
school stage
Grade 10
Exercise 1.(8 points)
Write the reaction equations that can be used to carry out the transformations: propane → 2-chloropropane → propene → 1,2-dichloropropane → propyne → propene → propanol-2 → 2-bromopropane → 2,3-dimethylbutane.
Task 2. (3 points)
KMnO 4 + H 2 O 2 + H 2 SO 4 \u003d K 2 SO 4 + MnSO 4 + H 2 O + O 2.
Task 3. (7 points)
When heating a sample of some solid BUT 5.6 g of solid formed B and gas AT. B dissolved in water, resulting in a solution containing 7.4 g of the substance G. AT passed through an excess of a solution of a substance D, resulting in the formation of 13.8 g of the substance E. When the latter interacts in an aqueous solution with G formed BUT and D. Define all substances.
Task 4.(5 points)
An excess of sodium hydroxide solution was added to a solution of 6.75 g of a mixture of copper (II) and zinc chlorides. The precipitate that formed was separated, calcined, and 2 g of dry residue were obtained. Determine the percentage composition of the mixture.
Task 5.(5 points)
In 1862, M. Berthelot synthesized gas by passing hydrogen through an electric arc between two carbon electrodes. The scientist determined its composition and gave it a name.
1) Determine the gas formula if the mass fractions of elements in the compound are: C - 92.3%, H - 7.7%. The relative vapor density of this substance for hydrogen is 13. Write down the structural formula of the substance and name it according to the systematic and trivial nomenclature.
2) Write down the reaction equation for obtaining this gas in industry.
3) Write down the reaction equations for the interaction of this substance with an excess of hydrogen and bromine.
4) Write down the reaction equation for the interaction of this gas with substance X, if during the reaction a yellowish substance Y is formed that can explode on impact.
Task 6.(8 points)
Four numbered tubes contain solutions of barium chloride, sodium carbonate, potassium sulfate and hydrochloric acid. Suggest a way to recognize substances without the use of additional reagents. Write reaction equations.
All-Russian Olympiad for schoolchildren in chemistry (2016-2017)
school stage
Grade 11
Exercise 1.(6 points)
Perform the following transformations. Name the products of the reaction, indicate the conditions for their implementation. Identify the unknown substance. (6 points)
C 6 H 14 → → → X→→ CH 3 COOCH 2 C 6 H 5
Task 2.(3 points)
Arrange the coefficients in the schemes of the following reactions using the electronic balance method
KMnO 4 + H 2 O 2 + H 2 SO 4 \u003d K 2 SO 4 + MnSO 4 + O 2 + ....
Task 3.(5 points)
The spacecraft crashed and landed on an unknown planet. The commander of the ship instructed one of the astronauts to determine the composition of the atmosphere. At the disposal of the astronaut were only an apple, a malachite box, lime water. He found that a cut apple does not change in the atmosphere of the planet, lime water does not become cloudy, and when malachite is heated, a red powder is formed. What conclusion did the astronaut come to and why.
Task 4.(5 points)
They burned a mixture of propane and ethane with a volume of 6.72 liters. The combustion product was passed into lime water. As a result, a precipitate weighing 80 g was formed. Determine the percentage composition of the mixture.
Task 5.(5 points)
They burned 2.3 g of an unknown substance, while forming 2.24 liters of carbon dioxide and 2.7 g of water. Write the molecular and structural formula of this substance if its nitrogen vapor density is 1.64.
Task 6.(8 points)
Five numbered tubes contain solutions of the following substances: KCL, KOH, K 2 CO 3 , H 2 SO 4 , ZnSO 4 . Suggest a way to recognize substances without the use of additional reagents. Write reaction equations.
Keys
All-Russian Olympiad for schoolchildren in chemistry (2016-2017)
school stage
Grade 8 (max. 24.5 points)
Exercise 1.3.5 points (0.5 points for each task)
Task 2.2 points (0.5 points for each element)
4VIB coordinates in the Periodic system mean the 4th period and VIB - group, element chromium 4VIIIB2 - 4th period, VIIIB2 - group, element nickel 6IB - 6th period, IB - group, element – gold 6IIB - 6th period, IIB - group, element mercury .
Task 3.6 points (1 point for each reaction)
Options for solving the task can be different, for example: CuCl 2 →Cu(OH) 2 →CuO (no more than three options)
1) CuCl 2 + 2NaOH → Cu(OH) 2 ↓ + 2NaCl 2) Cu(OH) 2 → CuO + H 2 O
Task 4.3 points
If you arrange the symbols of chemical elements in ascending order of their serial numbers, then from the set of letters written next to the chemical signs, you get the phrase: "A good friend is a real treasure."
Task 5.4 points
Wood shavings from small iron nails can be separated using a magnet - 1 point
Dissolve sugar with river sand in water - 1 point
Filter - 1 point
Evaporate water - 1 point
Task 6.6 points
1) Fe 3 O 4 2 points
2Fe2O33H2O
Keys
All-Russian Olympiad for schoolchildren in chemistry (2016-2017)
school stage
Grade 9 (max. 24 points)
Exercise 1.3 points (0.5 points for each task)
Task 27 points(Other formulations of the answer are allowed that do not distort its meaning)
Element X - sulfur S 0.5 points
S + O 2 = SO 2 1 point
2SO 2 + O 2 = 2SO 3 1 point
SO 3 + H 2 O \u003d H 2 SO 4 + Q 1 point
H 2 SO 4 + 2KOH = K 2 SO 4 + 2H 2 O 1 point
SO 2 + 2KOH = K 2 SO 3 + H 2 O 1 point
2KMnO 4 + 5K 2 SO 3 + 3 H 2 SO 4 = 2MnSO 4 + 6K 2 SO 4 + 3 H 2 O 1.5 points (equation
- 1 point, coefficients - 0.5 points)
Task 33 points
4 R + 5O 2 = 2 R 2 O 5 1 point
2 Ca + O 2 = 2 CaO 1 point
3 CaO + P 2 O 5 \u003d Ca 3 (PO 4) 2 1 point
Task 43 points
The number of protons is EQUAL to the number of electrons. Since (by condition) the number of protons is equal to the number of neutrons, therefore, neutrons = protons = electrons, therefore, 42:3=14. – 1 point
We know the number of protons, neutrons and electrons. The number of electrons is equal to the serial number of the element, therefore, this is the element numbered 14 - Si (silicon). – 1 point
28 Si - electrons - 14, protons - 14, neutrons - 28-14 = 14. - 1 point
Exercise 5 3 points
Me 2 O 3 + 3 H 2 SO 4 = Me 2 (SO 4) 3 + 3 H 2 O 1 point
1 mol 1 mol
(2x + 48) g/mol (2x + 288) g/mol
n(X) = m(X) / M(X)
n (Me 2 O 3) \u003d n (Me 2 (SO 4) 3)
9, 6 / 2x + 48 = 24 / 2x + 288;
x = 56 (Fe – iron) 2 points
Task 65 points
| A solution of phenolphthalein is prepared using ethyl alcohol and therefore has a characteristic odor | ||
| Phenolphthalein is added to three substances, a crimson color appears in sodium hydroxide. NaOH \u003d Na + + OH - when phenolphthalein is added, the appearance of a crimson color. | ||
| The solution stained with phenolphthalein is poured into two test tubes and two other solutions are added. NaOH + HCl \u003d H 2 O + NaCl - the disappearance of the crimson color In vitro - HCl | ||
| The remaining solution is sodium chloride |
Keys
All-Russian Olympiad for schoolchildren in chemistry (2016-2017)
school stage
Grade 10 (max. 36 points)
Exercise 1.8 points (1 for each equation)
Reaction equations:
1. CH 3 –CH 2 –CH 3 + Cl 2 → CH 3 –CHCl–CH 3 + HCl (hν, to)
2. CH 3 -CHCl -CH 3 + KOH (alcohol solution) → CH 3 -CH \u003d CH 2 + KCl + H 2 O
3. CH 3 -CH \u003d CH 2 + Cl 2 → CH 3 -CHCl -CH 2 Cl
4. CH 3 –CHCl–CH 2 Cl + 2 KOH (alcohol solution) → CH 3 –C≡CH + 2 KCl + 2 H 2 O
5. CH 3 -C≡CH + H 2 → CH 3 -CH \u003d CH 2 (to, p, kt)
6. CH 3 -CH \u003d CH 2 + HOH → CH 3 -CH (OH) - CH 3 (to, p, kt)
7. CH 3 -CH (OH) - CH 3 + HBr → CH 3 -CHBr - CH 3 + H 2 O (at to)
8. 2 CH 3 -CHBr -CH 3 + 2 Na → CH 3 -CH (CH 3) -CH (CH 3) -CH 3 + 2 NaBr
(Wurtz's reckoning)
Task 2.3 points
2KMnO 4 + 5H 2 O 2 + 3H 2 SO 4 = K 2 SO 4 + 2MnSO 4 + 8H 2 O + 5O 2 - 2 points
electronic balance:
Task 3.7 points (0.5 points for each substance, 1 point for the reaction)
All substances are defined: BUT - calcium carbonate, B - calcium oxide, AT - carbon dioxide, G - calcium hydroxide, D - potassium hydroxide, E - potassium carbonate
The reaction equations are composed: CaCO 3 → CaO + CO 2 CaO + H 2 O → Ca (OH) 2
CO 2 + 2KOH → K 2 CO 3 + H 2 OK 2 CO 3 + Ca (OH) 2 → CaCO 3 + 2KOH
Task 4.(5 points)
| CuCl 2 + 2 NaOH = Cu(OH) 2 ¯ + 2NaCL | ||
| ZnCL 2 + 4 NaOH = Na 2 [Zn(OH) 4] + 2NaCL | ||
| Cu(OH) 2 \u003d CuO + H 2 O | 0.5 - points |
|
| Calculate the amount of copper (II) oxide substance: N(CuO) = 2 g / 80g/mol = 0.025 mol | 0.5 - points |
|
| So CuCL 2 was also 0.025 mol | 0.5 - points |
|
| Hence the mass of CuCL 2 is: m (СuCL 2) \u003d 0.025 mol 136 g / mol \u003d 3.375 g | 0.5 - points |
|
| mass ZnCL 2 6.75 g - 3.375 g = 3.375 g | 0.5 - points |
|
| Mixture composition: 50% CuCL 2 and 50% ZnCL 2 | 0.5 - points |
|
Task 5.5 points
1) M r (C x H y) \u003d 13x2 \u003d 26 x: y \u003d 92.3 / 12: 7.7 / 1 \u003d 1: 1 CH is the simplest formula. 0.5 points
The true formula C 2 H 2 CH≡CH ethyne, acetylene 0.5 points
2) 2CH 4 → C 2 H 2 + 3H 2 (1500 0) 1 point
3) CH≡CH + 2H 2 → CH 3 - CH 3 (Temp., cat.) 1 point
CH≡CH + 2Br 2 → CHBr 2 - CHBr 2 1 point
4) CH≡CH + 2 OH → AgC ≡ CAg↓ + 4 NH 3 + 2 H 2 O 1 point
Task 6.8 points
Thought experiment table compiled
| a white precipitate | a white precipitate | without changes |
||
| a white precipitate | Without changes | colorless and odorless gas is released |
||
| a white precipitate | Without changes | Without changes |
||
| Without changes | A colorless and odorless gas is released | Without changes |
The reaction equations are given in molecular and ionic form:
BaCl 2 + Na 2 CO 3 → BaCO 3 ↓ + 2NaCl;
Na 2 CO 3 + 2HCl → 2NaCl + CO 2 + H 2 O
BaCl 2 + K 2 SO 4 = BaSO 4 ↓ + 2KCl;
Grading Guidelines
For compiling the table 1 point
For the thought experiment table - 4 points
For each correctly composed molecular equation, 1 point (3 equations) - 3 points
Keys
All-Russian Olympiad for schoolchildren in chemistry (2016-2017)
school stage
Grade 11 (max. 32 points)
Exercise 1.6 points
| C 6 H 14 → C 6 H 6 + 4 H 2 | ||
| C 6 H 6 + CH 3 Cl → C 6 H 5 - CH 3 + HCl (cat. AlCl 3 t) | ||
| C 6 H 5 - CH 3 + Cl 2 → C 6 H 5 - CH 2 Cl + HCl (in the light) | ||
| C 6 H 5 - CH 2 Cl + NaOH → C 6 H 5 - CH 2 OH + NaCl (aqueous solution) | ||
| C 6 H 5 - CH 2 OH + CH 3 COOH → CH 3 COOCH 2 C 6 H 5 + H 2 O (in the presence of H 2 SO 4) | ||
| X 1 - C 6 H 5 - CH 2 Cl |
Task 2.3 points
2KMnO 4 + 5H 2 O 2 + 3H 2 SO 4 = K 2 SO 4 + 2MnSO 4 + 5O 2 + 8H 2 O 2 points
electronic balance:
Mn +7 + 5e = Mn +2 ----x2 reduction, oxidizing agent 0.5 points
2O -1 - 2e = O2 0 -------x5 oxidation, reducing agent 0.5 points
Task 3.5 points
| The apple has not changed - there is no oxygen. | ||
| Lime water does not become cloudy - there is no carbon dioxide. | ||
| When heated, malachite decomposes into copper oxide, water, carbon dioxide. Cu 2 (OH)CO 3 → 2CuO + H 2 O + CO 2 | ||
| CuO + H 2 → Cu + H 2 O | ||
| CuO + CO → Cu + CO 2 | ||
| 3CuO + 2NH 3 → 3Cu + N 2 + 3H 2 O | ||
| The atmosphere may contain: hydrogen, carbon monoxide (II), nitrogen. |
Task 4.5 points
| C 2 H 6 + 7\2O 2 \u003d 2 CO 2 + 3H 2 O | 0.5 - points |
|
| C 3 H 8 + 2O 2 \u003d 2 CO 2 + 3H 2 O | 0.5 - points |
|
| CO 2 + Ca (OH) 2 \u003d CaCO 3 + H 2 O | 0.5 - points |
|
| υ (mixtures) = 6.72 L: 22.4 L/mol = 0.3 mol | ||
| υ (CaCO 3) \u003d 80 g: 100 g / mol \u003d 0. 8 mol | ||
| x + y \u003d 0.3 x \u003d 0.3 - y x \u003d 0.3 - y x \u003d 0.1 2x + 3y \u003d 0.8 2 (0.3 - y) + 3 y \u003d 0.8 y \u003d 0.2 ω (C 2 H 6) \u003d 0.1: 0.3 \u003d 0.33 or 33% ω (C 3 H 8) = 67% | 0.5 - points |
Task 5. 5 points
| Finding the molar mass of a M \u003d 28 * 1.64 \u003d 46 | ||
| Finding the mass of carbon M \u003d 2.24 \ 22.4 * 12 \u003d 1.2 | ||
| Finding the mass of hydrogen M=2.7*2\18=0.3 | ||
| 2.3- (1.2+0.3)=0.8- mass of oxygen | ||
| a:b:c= 1.2\12:0.3\1: 0.8\16= 0.1: 0.3:0.5= 2:6:1 | ||
Task 6.8 points
Drain the substances one by one
| Warming up a test tube | 1 point |
||||
| Gas evolution 1 point | |||||
| Warming up a test tube 1 point | Gas evolution | ||||
| Precipitation, then dissolution | |||||
| H 2 SO 4 +2 KOH \u003d 2H 2 O + K 2 SO 4 | |||||
| K 2 CO 3 + H 2 SO 4 \u003d K 2 SO 4 + H 2 O + CO 2 | |||||
| ZnSO 4 + 2 KOH \u003d Zn (OH) 2 + K 2 SO 4 | |||||
| 2 KOH \u003d Zn (OH) 2 \u003d K 2 | |||||
| Compiling a table | |||||
CORRESPONDENCE TOUR, 2012-2013 account. Year
№ | TASKS |
1. 11 | A copper plate weighing 15 g was placed in 150 g of a 50% solution of silver nitrate. After a while, the plate was removed from the solution, dried and weighed. Its mass turned out to be 23.5 g. What is the mass fraction of silver nitrate in the solution after the reaction. |
2 | The gas released during the interaction of 3.2 g of copper with 100 ml of 60% nitric acid (density 1.4 g/ml) was dissolved in 100 g of 15% sodium hydroxide solution. Calculate the mass fraction of sodium nitrite in the resulting solution. Give your answer as a percentage to the nearest tenth. |
3 | They burned a mixture of propane and ethane with a volume of 6.72 liters. The combustion product was passed into lime water. As a result, a precipitate weighing 80 g was formed. Determine the percentage composition of the mixture. |
4 | Establish a correspondence between the formula of the substance and the product that is formed on the cathode as a result of the electrolysis of its aqueous solution. FORMULA OF THE SUBSTANCE PRODUCT OF ELECTROLYSIS B) Na2CO3 3) oxygen D) CaCl2 4) carbon monoxide (IV) 5) nitric oxide (IV) |
5 | A mixture of silicon and coal weighing 20 g was treated with an excess of concentrated alkali solution. As a result of the reaction, hydrogen was released with a volume of 13.44 liters (normal conditions). Determine the mass fraction of silicon in the initial mixture. (Write down the number as a percentage to the nearest hundredth). |
6 | Hydrogen sulfide, released during the interaction of an excess of concentrated sulfuric acid with 1.44 g of magnesium, was passed through 160 g of a 1.5% bromine solution. Determine the mass of the precipitate formed in this case and the mass fraction of acid in the resulting solution. (Give the value of the mass fraction as a percentage with an accuracy of tenths). |
№ | TASKS |
2. 77 | Bottles without labels contain solutions of the following organic substances: formic acid, acetic acid, lactic acid, carbolic acid, salicylic acid ( about-hydroxybenzoic acid). Suggest an optimal (rational) way to determine these substances. Write down, if possible, the reaction equations. Specify signs. |
8 | Saponification of 14.8 g of glyceride required 72 ml of 10% NaOH solution (ρ = 1.12). Determine the formula of the ester taken for the reaction. Answer:1) - trimethylglyceride;2) - triethylglyceride;3) - dimethylethylglyceride. |
9 | With the complete combustion of 0.1 mol of open chain hydrocarbon, 5.4 ml of water is formed and 8.96 l (n.a.) of carbon monoxide (IV) is released. When this hydrocarbon interacts with an equimolar amount of chlorine, a predominantly symmetrical dichloroalkene is formed, in which the chlorine atoms are at the ends. Determine the structure of the hydrocarbon. Answer:1) - butin-1;2) - butadiene-1.3;3) - butin-2. |
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