Gaseous substances from the course of inorganic and organic chemistry

When preparing for the upcoming exams, graduates of the 9th and 11th grades need to study the issue of gaseous substances (physical properties, methods and methods of obtaining, their recognition and application). Having studied the topics of the specification of the exams of the OGE and the USE (on the websitewww. fipi. en ), we can say that there is practically no separate issue on gaseous substances (see table):

USE

№14 (Characteristic chemical properties of hydrocarbons: alkanes, cycloalkanes, alkenes, dienes, alkynes, aromatic hydrocarbons (benzene and toluene). Main methods for obtaining hydrocarbons (in the laboratory);№26 (Rules for working in the laboratory. Laboratory glassware and equipment. Safety rules for working with caustic, combustible and toxic substances, household chemicals. Scientific methods for studying chemicals and transformations. Methods for separating mixtures and purifying substances. The concept of metallurgy: general methods for obtaining metals General scientific principles of chemical production (on the example of industrial production of ammonia, sulfuric acid, methanol) Chemical pollution of the environment and its consequences Natural sources of hydrocarbons, their processing High-molecular compounds Polymerization and polycondensation reactions Polymers Plastics, fibers, rubbers)

So, in option No. 3 (Chemistry. Preparation for the OGE-2017. 30 training materials according to the demo version of 2017. Grade 9: teaching aid / edited by V.N. Doronkin. - Rostov n / D: Legion, 2016. - 288 p.), students were asked to answer the following question (No. 13):

Are the following judgments about the methods of obtaining substances correct?

A. Ammonia cannot be collected by displacing water.

B. Oxygen cannot be collected by displacing water.

1) only A is true

2) only B is true

3) both statements are correct

4) both judgments are wrong

To answer the question, the guys should know the physical and chemical properties of ammonia and oxygen. Ammonia interacts very well with water, therefore, it cannot be obtained by the method of water displacement. Oxygen dissolves in water, but does not interact with it. Therefore, it can be obtained by the method of water displacement.

In option No. 4 (Chemistry. Preparation for the Unified State Examination-2017. 30 training options for the demo version for 2017: educational and methodological manual / edited by V.N. Doronkin. - Rostov n / D: Legion, 2016. - 544 p. ) students are asked to answer the following question (No. 14):

From the proposed list, select two substances that are formed when a mixture of solid potassium acetate and potassium hydroxide is heated:

1) hydrogen;

2) methane;

3) ethane;

4) carbon dioxide;

5) potassium carbonate

Answer: 2 (decarboxylation reaction)

Moreover, in order to pass the exam, the guys need to know what is the raw material for obtaining one or another gaseous substance. For example, in the same book, edited by Doronkin, question No. 26 (option 8) sounds like this:

Establish a correspondence between the substance obtained in industry and the raw material used to obtain it: for each position indicated by a letter, select the corresponding position indicated by a number:

Write in the table the selected numbers under the corresponding letters:

Answer:

In option No. 12, students are asked to recall the scope of some gaseous substances:

Establish a correspondence between the substance and its scope: for each position indicated by a letter, select the corresponding position indicated by a number:

Answer:

With the guys taking the exam in chemistry in the 9th grade, in the preparation for the exam, we fill out the following table (in the 11th grade we repeat it and expand it):

Hydrogen

The lightest gas, 14.5 times lighter than air, with air in the ratio of two volumes of hydrogen to one volume of oxygen forms "explosive gas"

1. By the interaction of alkali and alkaline earth metals with water:

2 Na + 2 H 2 O = 2 NaOH + H 2

2. Interaction of metals (up to hydrogen) with hydrochloric acid (any concentration) and dilute sulfuric acid:

Zn + 2 HCl = ZnCl 2 + H 2

3. Interaction of transition (amphoteric) metals with a concentrated alkali solution when heated:

2Al + 2NaOH ( conc ) + 6H 2 O = 2Na + 3H 2

4. Decomposition of water under the influence of electric current:

2H 2 O=2H 2 + O 2

According to the characteristic sound of the explosion: a vessel with hydrogen is brought to the flame (deaf clap - pure hydrogen, "barking" sound - hydrogen mixed with air):

2H 2 + O 2 2H 2 O

Hydrogen burner, margarine production, rocket fuel, production of various substances (ammonia, metals, e.g. tungsten, hydrochloric acid, organic substances)

Oxygen

Colorless gas, odorless; in the liquid state it has a light blue color, in the solid state it is blue; more soluble in water than nitrogen and hydrogen

1. By decomposition of potassium permanganate:

2 KMnO 4 = K 2 MNO 4 + MNO 2 + O 2

2. By decomposition of hydrogen peroxide:

2 H 2 O 2 2 H 2 + O 2

3. Decomposition of Bertolet salt (potassium chlorate):

2KClO 3 = 2KCl + 3O 2

4. Decomposition of nitrates

5. Decomposition of water under the influence of electric current:

2 H 2 O = 2 H 2 + O 2

6. Photosynthesis process:

6 CO 2 + 6 H 2 O = C 6 H 12 O 6 + 6O 2

The flash of a smoldering splinter in a container of oxygen

In metallurgy, as an oxidizer for rocket fuel, in aviation for breathing, in medicine for breathing, in blasting, for gas cutting and welding of metals

Carbon dioxide

Colorless gas, odorless, 1.5 times heavier than air. Under normal conditions, one volume of carbon dioxide dissolves in one volume of water. At a pressure of 60 atm, it turns into a colorless liquid. When liquid carbon dioxide evaporates, part of it turns into a solid snow-like mass, which is pressed in industry - “dry ice” is obtained.

1. Limestone calcination industry:

CaCO 3 CaO + CO 2

2. The action of hydrochloric acid on chalk or marble:

CaCO 3 + 2HCl = CaCl 2 + H 2 O+CO 2

With the help of a burning splinter that goes out in an atmosphere of carbon dioxide, or by clouding lime water:

CO 2 + Ca(Oh) 2 = CaCO 3 ↓ + H 2 O

For creating "smoke" on stage, storing ice cream, in fizzy drinks, in foam fire extinguishers

Ammonia

A colorless gas with a pungent odor, almost 2 times lighter than air. You can not inhale for a long time, because. he is poisonous. Easily liquefies at normal pressure and temperature -33.4 about C. When liquid ammonia evaporates from the environment, a lot of heat is absorbed, so ammonia is used in refrigeration. Highly soluble in water: at 20 about C About 710 volumes of ammonia dissolve in 1 volume of water.

1. In industry: at high temperatures, pressure and in the presence of a catalyst, nitrogen reacts with hydrogen, forming ammonia:

N 2 +3 H 2 2 NH 3 + Q

2. In the laboratory, ammonia is obtained by the action of slaked lime on ammonium salts (most often ammonium chloride):

Ca(OH) 2 + 2NH 4 Cl CaCl 2 + 2NH 3 + 2H 2 O

1) by smell;

2) by changing the color of wet phenolphthalein paper (turned crimson);

3) by the appearance of smoke when bringing a glass rod moistened with hydrochloric acid

1) in refrigeration units; 2) production of mineral fertilizers;

3) production of nitric acid;

4) for soldering; 5) receiving explosives; 6) in medicine and in everyday life (ammonia)

Ethylene

Under normal conditions, it is a colorless gas with a slight odor, partially soluble in water and ethanol. Let's well dissolve in diethyl ether and hydrocarbons. It is a phytohormone. Has narcotic properties. The most produced organic matter in the world.

1) In the ethane dehydrogenation industry:

CH 3 -CH 3 CH 2 =CH 2 + H 2

2) Ethylene is produced in the laboratory in two ways:

a) depolymerization of polyethylene:

(-CH 2 -CH 2 -) n nCH 2 =CH 2

b) catalytic dehydration of ethyl alcohol (white clay or pure alumina and concentrated sulfuric acid are used as a catalyst):

C 2 H 5 OHCH 2 =CH 2 + H 2 O

Oxygen

+

upside down

+

Upside down

Carbon dioxide

+

upside down

-

Ammonia

+

Upside down

-

Ethylene

+

Upside down and slanted

-

Thus, in order to successfully pass the OGE and the Unified State Examination, students need to know the methods and methods for obtaining gaseous substances. The most common of these are oxygen, hydrogen, carbon dioxide and ammonia. In the 11th grade textbook, children are offered practical work No. 1, which is called "Receiving, collecting and recognizing gases." It proposed five options - obtaining five different gaseous substances: hydrogen, oxygen, carbon dioxide, ammonia and ethylene. Of course, in a lesson lasting 45 minutes, all 5 options are simply unrealistic to complete. Therefore, before starting this work, students at home fill out the above table. Thus, when filling out the table, the guys at home repeat the methods and methods for obtaining gaseous substances (chemistry course of grades 8, 9 and 10) and come to the lesson already theoretically aware. For one topic, graduates receive two grades. The work is big, but the guys are happy to do it. And the incentive is - a good mark in the certificate.

PRACTICAL WORK (1 h) Grade 8

The work is carried out by the students independently under the supervision of the teacher.
I offer the result of my many years of work on the preparation and conduct of practical work in a comprehensive school in chemistry lessons in grades 8–9:

• Obtaining and properties of oxygen,
• "Preparation of salt solutions with a certain mass fraction of the dissolved substance",
• "Generalization of information about the most important classes of inorganic compounds",
• "Electrolytic dissociation",
• "Oxygen subgroup" (see the next issue of the newspaper "Chemistry").

All of them are tested by me in the classroom. They can be used in the study of the school course of chemistry both according to the new program of O.S. Gabrielyan, and according to the program of G.E. Rudzitis, F.G. Feldman.
A student experiment is a type of independent work. The experiment not only enriches students with new concepts, skills, skills, but also is a way to verify the truth of the knowledge they have acquired, contributes to a deeper understanding of the material, the assimilation of knowledge. It allows you to more fully implement the principle of variability in the perception of the surrounding world, since the main essence of this principle is the connection with life, with the future practical activities of students.

Goals. Be able to receive oxygen in the laboratory and collect it by two methods: air displacement and water displacement; confirm experimentally the properties of oxygen; know the safety rules.
Equipment. A metal stand with a foot, a spirit lamp, matches, a test tube with a gas outlet tube, a test tube, a ball of cotton wool, a pipette, a beaker, a splinter, a dissecting needle (or wire), a crystallizer with water, two conical flasks with stoppers.
Reagents. KMnO 4 crystalline (5–6 g), Ca (OH) 2 lime water, charcoal,
Fe (steel wire or paper clip).

Safety regulations.
Handle chemical equipment with care!
Remember! The test tube is heated, holding it in an inclined position, along its entire length with two or three movements in the flame of an alcohol lamp. When heating, point the opening of the test tube away from yourself and your neighbors.

Previously, students receive homework related to the study of the content of the upcoming work according to the instructions, while simultaneously using the materials of the 8th grade textbooks by O.S. Gabrielyan (§ 14, 40) or G.E. Rudzitis, F.G. Feldman (§ 19 , 20). In notebooks for practical work, they write down the name of the topic, the goal, list the equipment and reagents, draw up a table for the report.

DURING THE CLASSES

One experience I put higher
than a thousand opinions
born only
imagination.

M.V. Lomonosov

Obtaining oxygen
air displacement method

(10 minutes)

1. Potassium permanganate (KMnO 4) place in a dry test tube. Place a loose ball of cotton wool at the opening of the test tube.
2. Close the test tube with a stopper with a gas outlet tube, check for tightness (Fig. 1).

Rice. one. Instrument check for tightness

(Teacher's explanations on how to check the device for leaks.) Fix the device in the tripod leg.

3. Lower the gas outlet tube into the glass, without touching the bottom, at a distance of 2–3 mm (Fig. 2).

4. Warm up the substance in the test tube. (Remember safety regulations.)
5. Check for the presence of gas with a smoldering splinter (charcoal). What are you watching? Why can oxygen be collected by air displacement?
6. Collect the resulting oxygen in two flasks for the following experiments. Close the flasks with stoppers.
7. Prepare a report using the table. 1, which you place on the spread of your notebook.

Obtaining oxygen
water displacement method

(10 minutes)

1. Fill a test tube with water. Close the vial with your thumb and turn it upside down. In this position, lower the hand with the test tube into the crystallizer with water. Bring a test tube to the end of the gas outlet tube without removing it from the water (Fig. 3).

2. When the oxygen has forced the water out of the tube, close it with your thumb and remove it from the water. Why can oxygen be collected by displacing water?
Attention! Remove the gas outlet tube from the crystallizer, continuing to heat the tube with KMnO 4 . If this is not done, then the water will be thrown into a hot test tube. Why?

Combustion of coal in oxygen

(5 minutes)

1. Fix the coal on a metal wire (dissecting needle) and bring it into the flame of an alcohol lamp.
2. Lower the red-hot coal into the flask with oxygen. What are you watching? Give an explanation (Figure 4).

3. After removing the unburned coal from the flask, pour 5-6 drops of lime water into it
Ca(OH) 2 . What are you watching? Give an explanation.
4. Issue a report on the work in the table. one.

Burning steel (iron) wire
in oxygen

(5 minutes)

1. Attach a piece of a match to one end of the steel wire. Light a match. Immerse the wire with the burning match into the flask with oxygen. What are you watching? Give an explanation (Figure 5).

2. Issue a report on the work in the table. one.

Table 1

Operations in progress (what they were doing)	Figures with designations of initial and received substances	Observations. Conditions carrying out reactions. Reaction equations	Explanations of observations. findings
Assembly of the device for obtaining oxygen. Checking the device for leaks
Obtaining oxygen from KMnO 4 when heated
Proof of oxygen production with smoldering splinter
Characteristics of the physical properties of O 2. Collecting O 2 by two methods: air displacement, water displacement
Characteristic chemical properties of O 2. Interaction with simple substances burning coal, burning iron (steel wire, paper clip)

Make a written general conclusion about the work done (5 min).

CONCLUSION. One of the ways to obtain oxygen in the laboratory is the decomposition of KMnO 4 . Oxygen is a colorless and odorless gas, 1.103 times heavier than air ( M r(O 2) \u003d 32, M r(air) \u003d 29, from which follows 32/29 1.103), slightly soluble in water. It reacts with simple substances, forming oxides.

Put the workplace in order (3 min): disassemble the appliance, arrange the dishes and accessories in their places.

Submit your notebooks for review.

Homework.

Task. Determine which of the iron compounds - Fe 2 O 3 or Fe 3 O 4 - is richer in iron?

Given:	To find:
Fe 2 O 3, Fe 3 O 4 .	(Fe) in Fe 2 O 3, "(Fe) to Fe 3 O 4

Decision

(X) = n A r(X)/ M r, where n- the number of atoms of the element X in the formula of the substance.

M r(Fe 2 O 3) \u003d 56 2 + 16 3 \u003d 160,

(Fe) \u003d 56 2/160 \u003d 0.7,
(Fe) = 70%,

M r(Fe 3 O 4) \u003d 56 3 + 16 4 \u003d 232,
"(Fe) \u003d 56 3/232 \u003d 0.724,
"(Fe) = 72.4%.

Answer. Fe 3 O 4 is richer in iron than Fe 2 O 3 .

During practical work, the teacher monitors the correctness of the performance of techniques and operations by students and notes in the skill record card (Table 2).

table 2

Skill record card

Operations of practical work	Surnames of students
	BUT	B	AT	G	D	E
Assembly of the device for obtaining oxygen
Checking the device for leaks
Fixing the test tube in the leg of the tripod
Alcohol lamp handling
Heating a test tube with KMnO 4
Checking the release of O 2
Collecting O 2 in a vessel by two methods: air displacement, water displacement
coal burning
Combustion of Fe (steel wire)
Experimental culture
Making work in a notebook

Sample report on the practical work done (Table 1)

O 2 is obtained in the laboratory by decomposition of KMnO 4 when heated Proof of obtaining oxygen by means of
smoldering splinter smoldering splinter
(charcoal) lights up brightly
in O 2 The resulting gas O 2 supports combustion Characteristic
physical properties of O 2. Collecting O 2 by two methods:
air displacement (a),
water displacement (b)

Oxygen displaces air and water from vessels Oxygen is a colorless and odorless gas
slightly heavier than air, so
it is collected in a vessel placed on the bottom. Oxygen is slightly soluble in water Characteristics of the chemical properties of O 2. Interaction with simple substances: combustion of coal (a), combustion of iron (steel wire, paper clip, shavings) (b)

A red-hot coal burns brightly in O 2:

Lime water becomes cloudy, because a water-insoluble precipitate of CaCO 3 is formed:
CO 2 + Ca (OH) 2 CaCO 3 + H 2 O. Iron burns with a bright flame in oxygen:

O 2 interacts
with simple
substances - metals and non-metals. The formation of a white precipitate confirms the presence of CO 2 in the flask

If a dry gas outlet tube is required for the experiment, then proceed as follows. A rubber tube with a glass tip is put on the free end of the gas outlet tube. When testing the tightness of the device, the removable tip will get wet, and the gas outlet tube will remain dry.

Gas can be collected in a container in a variety of ways. The two most common are the air displacement method and the water displacement method. Each of them has its own advantages and disadvantages, and the choice of method is largely determined by the properties of the gas to be collected.

Air displacement method

Any gas can be collected by this method, but here the problem arises of accurately determining the moment when all the air from the receiver vessel will be displaced by the collected gas.

Before collecting gas by displacement of air, it is necessary to find out whether it is heavier or lighter than air. The position of the receiving vessel will depend on this (Fig.). To do this, calculate the relative density of the gas in air according to the formula: D air. (X) = Mr(X)/29, where Mr is the relative molecular weight of the collected gas, 29 is the relative molecular weight of the air. If the calculated value turns out to be less than one, then the gas is lighter than air, and the receiving vessel must be placed with the hole down (Fig. 57, a). If the relative density of the gas in air is greater than one, then the gas is heavier than air, and the receiving vessel should be positioned with the hole up (Fig. 57, b).

Rice. 57. The position of the receiver vessel (1): a - for a gas that is lighter than air; b - for a gas that is heavier than air.

The filling of the vessel can be controlled in different ways depending on which gas is being collected. For example, colored nitric oxide (IV) is easily detected by its red-brown color. To detect oxygen, a smoldering splinter is used, which is brought to the edge of the vessel, but not brought inside.

Water displacement method.

When using this method, it is much easier to control the filling of the receiving vessel with gas. However, this method has a serious limitation - it cannot be used if the gas dissolves in water or reacts with it .

To collect gas by displacement of water, it is necessary to have a wide vessel, for example, a crystallizer, filled 2/3 with water. The receiving vessel, such as a test tube, is filled to the top with water, closed with a finger, quickly turned upside down and lowered into the crystallizer. When the opening of the test tube is under water, the opening of the test tube is opened and a gas outlet tube is inserted into the test tube (Fig. 58).

Rice. 58. Device for collecting gas by the method of water displacement: 1 - receiver tube filled with water; 2 - crystallizer.

After all the water has been displaced from the tube by the gas, the opening of the test tube closed under water stopper and removed from the crystallizer.

If the gas, which is collected by the displacement of water, is obtained by heating, the following rule must be strictly observed:

Do not stop heating the test tube with starting substances if the gas outlet tube is under water!

Registration of the results of the experiment

The form of recording the results obtained during the performance of a chemical experiment is not regulated by anyone. But the protocol of the experiment must necessarily include the following items: the name of the experiment and the date it was carried out, the purpose of the experiment, the list of equipment and reagents that were used, the drawing or diagram of the device, a description of the actions that were performed during the work, observations, equations of ongoing reactions, calculations , if they were made during the performance of the work, conclusions.

Form of the report on the carried out practical work.

Write down the date of the experiment and the name of the experiment.

State the purpose of the experiment.

Briefly write down everything you did.

Make a drawing of the experiment or draw the device you used. Try to keep the drawing clear. Be sure to add explanatory notes to the picture. For the image of colored substances, use colored pencils or felt-tip pens.

Write down your observations, i.e. describe the conditions for the occurrence and signs of chemical reactions.

Write equations for all the chemical reactions that took place during the experiment. Don't forget to set the odds.

Draw a conclusion from experience (or work).

You can draw up a report on the work as a sequential description of actions and observations, or in the form of a table:

Experience no...

Experience Description	Drawing experience	Signs of reactions	Findings. Reaction equations

When solving experimental problems related to the recognition and identification of substances, it is convenient to format the report in the form of another table:

Procedure	Reagent	Tube number			Conclusion

Topic 1. Basic concepts and laws of chemistry.

Laboratory experiments.

Examples of physical phenomena.

Experience No. 1. Heating glass (glass tube)

in the flame of an alcohol lamp.

Equipment and reagents: glass tube, spirit lamp, matches, asbestos mesh.

1. Hold the glass tube by its ends with both hands.

2. Bring the middle part of the tube into the flame of the spirit lamp. Remember that the top of the flame is the hottest.

3. Rotate the tube without taking it out of the flame of the spirit lamp (Fig. 59).

4. When the glass becomes very hot (after 3-4 minutes), try to bend the tube without applying excessive force.

Rice. 59. Bending a glass tube.

Lay the glass tube on the asbestos mesh. Be careful: hot glass looks the same as cold glass!

1) Has the glass changed?

2) Was a new substance obtained by heating the glass tube?

Experience No. 2. Melting of paraffin.

Equipment and reagents: crucible or glass plate, spirit lamp, matches, crucible tongs or test tube holder, asbestos mesh, paraffin.

Instructions for performing the experiment.

1. Put a small piece of paraffin into the crucible (or onto a glass plate).

2. Take the crucible (or glass plate) with crucible tongs (or fix it in a test tube holder).

3. Insert the wax crucible (or glass plate) into the top of the spirit lamp flame. Watch the changes carefully.

4. After melting the paraffin, place the crucible (or glass plate) on the asbestos mesh and turn off the spirit lamp.

5. When the crucible (or glass plate) has cooled, examine the substance that is in the crucible (or glass plate).

1) Has the paraffin changed?

2) Was a new substance obtained by heating paraffin?

3) What is this phenomenon: physical or chemical?

Examples of chemical phenomena.

Experience No. 3. Ignition of a copper plate or wire

in the flame of an alcohol lamp.

Equipment and reagents: spirit lamp, matches, crucible tongs or test tube holder, asbestos mesh, copper wire or plate.

Instructions for performing the experiment.

1. Take a copper plate (or copper wire) with crucible tongs.

2. Insert a copper plate into the top of the spirit lamp flame and heat it up.

3. After 1-2 minutes, remove the plate from the flame and clean off the formed black coating from it with a knife or a splinter on a clean sheet of paper.

4. Repeat the heating and again clean off the resulting plaque.

5. Compare the resulting black coating with a copper plate.

1) Has the copper plate changed when heated?

2) Was a new substance formed when the copper plate was heated?

3) What is this phenomenon: physical or chemical?

Experience No. 4. The effect of hydrochloric acid on chalk or marble.

Equipment and reagents: chemical beaker with a volume of 50 ml, marble (small pieces or crumbs), hydrochloric acid solution (1: 3), matches.

Instructions for performing the experiment.

1. In a beaker, place 2-3 small pieces of marble the size of a pea. Be careful not to break the bottom of the glass.

2. Pour enough hydrochloric acid into a glass so that the pieces of marble are completely covered with it. What are you watching?

3. Light a match and put it into the cup. What are you watching?

4. Draw the experiment, write down your observations.

1) Was a new substance formed when hydrochloric acid was added to marble? What is this substance?

2) Why did the match go out?

3) What is this phenomenon: physical or chemical?

Types of chemical reactions.

Test "Nitrogen and its compounds"

Option 1 1. The strongest molecule a) H 2; b) F 2 ; c) O 2; d) N 2 . 2. Phenolphthalein color in ammonia solution: a) crimson; b) green; c) yellow; d) blue. 3. The oxidation state is +3 at the nitrogen atom in the compound: a) NH 4 NO 3; b) NaNO 3 ; c) NO 2; d) KNO 2. 4. During thermal decomposition of copper (II) nitrate, the following are formed:a) copper (II) nitrite and O 2 ;b) nitric oxide(IV) and O 2 ;c) copper(II) oxide, brown gas NO 2 and O 2 ; d) copper (II) hydroxide, N 2 and O 2. 5. Which ion is formed by the donor-acceptor mechanism? a) NH 4 + ; b) NO 3 - ; c) Cl - ; d) SO 4 2–. 6. Specify strong electrolytes: a) nitric acid; b) nitrous acid; c) an aqueous solution of ammonia; d) ammonium nitrate. 7. Hydrogen is released during the interaction: a) Zn + HNO 3 (razb.); b) Cu + HCl (solution); c) Al + NaOH + H 2 O; d) Zn + H 2 SO 4 (razb.); e) Fe + HNO 3 (conc.). 8. Write an equation for the reaction of zinc with very dilute nitric acid if one of the reaction products is ammonium nitrate. Specify the coefficient in front of the oxidizing agent. 9.

Name the substances A, B, C. Option 2 1. It is impossible to collect by the method of displacement of water: a) nitrogen; b) hydrogen; c) oxygen; d) ammonia. 2. The reagent for the ammonium ion is a solution of: a) potassium sulfate; b) silver nitrate; c) sodium hydroxide; d) barium chloride. 3. When interacting with HNO 3 (conc.) gas is formed with copper shavings: a) N 2 O; b) NH 3; c) NO 2 ; d) H 2 . 4. Thermal decomposition of sodium nitrate produces: a) sodium oxide, brown gas NO 2, O 2; b) sodium nitrite and O 2; c) sodium, brown gas NO 2, O 2; d) sodium hydroxide, N 2, O 2. 5. The degree of nitrogen oxidation in ammonium sulfate: a) -3; b) -1; c) +1; d) +3. 6. With which of the following substances does concentrated HNO react? 3 under normal conditions? a) NaOH; b) AgCl; c) Al; d) Fe; e) Cu. 7. Specify the number of ions in the abbreviated ionic equation for the interaction of sodium sulfate and silver nitrate: a) 1; b) 2; in 3; d) 4. 8. Write an equation for the interaction of magnesium with dilute nitric acid if one of the reaction products is a simple substance. Specify the coefficient in the equation in front of the oxidizing agent. 9. Write reaction equations for the following transformations:

Name the substances A, B, C, D.

Answers

Option 1 1 - G; 2 - a; 3 - G; 4 - in; 5 - a; 6 - a, d; 7 - c, d; 8 – 10,

9. A - NH 3, B - NH 4 NO 3, C - NO,

Option 2 1 - d; 2 - in; 3 - in; 4 - b; 5 - a; 6 – a, e; 7 - in,

2Ag + + SO 4 2– = Ag 2 SO 4;

8 – 12, 9. A - NO, B - NO 2, C - HNO 3, D - NH 4 NO 3,

Kipp apparatus used to produce hydrogen, carbon dioxide and hydrogen sulfide. The solid reagent is placed in the middle spherical reservoir of the apparatus on a plastic annular insert, which prevents the solid reagent from entering the lower reservoir. Zinc granules are used as a solid reagent for producing hydrogen, pieces of marble are used for carbon dioxide, and pieces of iron sulfide are used for hydrogen sulfide. The solids to be poured should be about 1 cm 3 in size. It is not recommended to use powder, as the gas current will turn out to be very strong. After loading the solid reagent into the apparatus, a liquid reagent is poured through the upper neck (for example, a dilute solution of hydrochloric acid in the production of hydrogen, carbon dioxide and hydrogen sulfide). The liquid is poured in such an amount that its level (with the gas outlet valve open) reaches half of the upper spherical expansion of the lower part. The gas is passed through for 5-10 minutes to force the air out of the apparatus, then the gas outlet valve is closed, a safety funnel is inserted into the upper throat. The gas outlet tube is connected to the device where the gas must be passed.

When the tap is closed, the released gas displaces the liquid from the spherical expansion of the apparatus, and it stops working. When the tap is opened, the acid again enters the tank with a solid reagent, and the apparatus starts to work. This is one of the most convenient and safe methods for obtaining gases in the laboratory.

Collect gas in a vessel possible by various methods. The two most common methods are the water displacement method and the air displacement method. The choice of method is dictated by the properties of the gas to be collected.

Air displacement method. Almost any gas can be collected by this method. Before taking a gas, it is necessary to determine whether it is lighter than air or heavier. If the relative density of the gas in air is greater than one, then the receiving vessel should be kept with the hole up, since the gas is heavier than air and will sink to the bottom of the vessel (for example, carbon dioxide, hydrogen sulfide, oxygen, chlorine, etc.). If the relative density of the gas in air is less than unity, then the receiving vessel should be kept with the hole down, since the gas is lighter than air and will rise up the vessel (for example, hydrogen, etc.). The filling of the vessel can be controlled in different ways, depending on the properties of the gas. For example, to determine oxygen, a smoldering torch is used, which, when brought to the edge of the vessel (but not inside!) Flashes; when determining carbon dioxide, the hot torch goes out.

Water displacement method. This method can only collect gases that do not dissolve in water (or slightly dissolve) and do not react with it. To collect gas, a crystallizer is needed, 1/3 filled with water. The receiver vessel (most often a test tube) is filled to the top with water, closed with a finger and lowered into the crystallizer. When the opening of the vessel is under water, it is opened and a gas outlet tube is inserted into the vessel. After all the water is displaced from the vessel by gas, the hole is closed under water with a cork and the vessel is removed from the crystallizer.

Checking the gas for purity. Many gases burn in air. If you set fire to a mixture of combustible gas with air, an explosion will occur, so the gas must be checked for purity. The test consists in burning a small portion of gas (about 15 ml) in a test tube. To do this, the gas is collected in a test tube and set on fire from the flame of an alcohol lamp. If the gas does not contain air impurities, then combustion is accompanied by a slight pop. If a sharp barking sound is heard, then the gas is contaminated with air and needs to be cleaned.