Obtaining gaseous substances. Determination of the nature of the medium of a solution of acids and alkalis using indicators. Qualitative reactions to ions in solution (chloride, sulfate, carbonate ions, ammonium ion). Obtaining gaseous substances Chemical reactions in ra

Depending on which H + or OH - ions are in excess in an aqueous solution, the following types (characters) of solution media are distinguished:

1) sour

2) alkaline

3) neutral

When acidic environment the solution contains an excess of hydrogen cations H +, and the concentration of hydroxide ions is close to zero.

When alkaline environment there is an excess of hydroxide ions OH - in the solution, and the concentration of H + cations is close to zero.

When neutral environment solution concentration of ions H + and OH - are equal to each other and practically equal to zero (0.0000001 mol / l).

There are some organic matter, the color of which changes depending on the nature of the environment. This phenomenon is widely used in chemistry. Some of the most common indicators are litmus, phenolphthalein, and methyl orange (methyl orange). The color of these substances, depending on the nature of the environment, is presented in the following table:

	indicator color
indicator	in a neutral environment	in an acidic environment	in an alkaline environment
litmus	purple	red	blue
phenolphthalein	colorless	colorless	crimson
methyl orange (methyl orange)	orange	pink	yellow

As you can see, the specific property of phenolphthalein is that this indicator does not allow distinguishing between neutral and acidic media - in both media it is not colored in any way. This property is undoubtedly a disadvantage, however, phenolphthalein is widely used due to its exceptional sensitivity to even a slight excess of OH - ions.

Obviously, with the help of indicators, it is possible to distinguish acids, alkalis and distilled water from each other. However, it should be remembered that acidic, alkaline and neutral media can be observed not only in solutions of acids, alkalis and distilled water. The environment of solutions can also be different in salt solutions, depending on their relationship to hydrolysis.

So, for example, a sodium sulfite solution from a sodium sulfate solution can be distinguished using phenolphthalein. Sodium sulfite is a salt formed by a strong base and a weak acid, so its solutions will have an alkaline reaction of the medium. Phenolphthalein turns crimson in its solution. Sodium sulfate is formed by a strong base and a strong acid, i.e. does not undergo hydrolysis, and its aqueous solutions will have a neutral reaction of the environment. In the case of sodium sulfate solution, phenolphthalein will remain colorless.

In task 18 of the OGE in chemistry, we demonstrate knowledge of indicators and pH, as well as qualitative reactions to ions in solution.

Theory for task number 18 of the OGE in chemistry

Indicators

Indicator - chemical substancewhich changes color depending on the pH of the medium.

The most famous indicators are phenolphthalein, methyl orange, litmus and universal indicator. Their colors depending on the environment in the picture below:

And here are the colors of the indicators in more detail with real life examples:

We figured out the indicators, let's move on to qualitative reactions to ions.

Qualitative reactions to ions

Qualitative reactions for cations and anions are presented in the table below.

How to properly cope with task 18 in the OGE test in chemistry?

To do this, you need to select a qualitative reaction to one of the options provided and make sure that this reagent does not react with the second substance.

Analysis of typical options for task No. 18 of the OGE in chemistry

The first variant of the task

Establish a correspondence between two substances and a reagent with which you can distinguish between these substances.

Substances:

A) Na2CO3 and Na2SiO3

B) К2CO3 and Li2CO3

C) Na2SO4 and NaOH

Reagent:

1) CuCl2

4) K3PO4

Let's consider each case.

Na2CO3 and Na2SiO3

1. the reaction does not proceed with copper chloride in both cases, since copper carbonate and silicate decomposes in an aqueous solution
2. with hydrochloric acid, in the case of sodium carbonate, gas is released, and in the case of silicate, a precipitate forms - this qualitative reaction to silicates
3. there are also no qualitative reactions to sodium with phosphate

К2CO3 and Li2CO3

1. these substances do not react with copper chloride (in fact, a precipitate of copper hydroxide precipitates, but this reaction cannot distinguish the two reagents)
2. both react with hydrochloric acid with the release of carbon dioxide
3. these substances do not react with magnesium oxide, and magnesium oxide does not enter into ion exchange reactions
4. with phosphate lithium precipitates as phosphate but no potassium

We have the last option - copper chloride. Indeed, copper hydroxide precipitates with sodium hydroxide, but the reaction does not proceed with sulfate.

Chemically, the pH of a solution can be determined using acid-base indicators.

Acid-base indicators are organic substances, the color of which depends on the acidity of the medium.

The most common indicators are litmus, methyl orange, phenolphthalein. Litmus turns red in an acidic medium, and blue in an alkaline medium. Phenolphthalein in an acidic medium is colorless, in an alkaline medium it turns crimson. Methyl orange turns red in an acidic medium, and yellow in an alkaline medium.

In laboratory practice, a number of indicators are often mixed, selected so that the color of the mixture changes over a wide range of pH values. With their help, you can determine the pH of the solution with an accuracy of one. These mixtures are called universal indicators.

There are special devices - pH meters, with which you can determine the pH of solutions in the range from 0 to 14 with an accuracy of 0.01 pH units.

Hydrolysis of salts

When some salts are dissolved in water, the equilibrium of the water dissociation process is disturbed and, accordingly, the pH of the medium changes. This is because salts react with water.

Hydrolysis of salts – chemical exchange interaction of ions of a dissolved salt with water, leading to the formation of weakly dissociating products (molecules of weak acids or bases, anions of acid salts or cations of basic salts) and accompanied by a change in the pH of the medium.

Consider the process of hydrolysis depending on the nature of the bases and acids that form the salt.

Salts formed by strong acids and strong bases (NaCl, kno3, Na2so4, etc.).

Let's admitthat when sodium chloride interacts with water, a hydrolysis reaction occurs with the formation of an acid and a base:

NaCl + H 2 O ↔ NaOH + HCl

For a correct understanding of the nature of this interaction, we write the reaction equation in ionic form, taking into account that water is the only weakly dissociating compound in this system:

Na + + Cl - + HOH ↔ Na + + OH - + H + + Cl -

With the reduction of identical ions in the left and right sides of the equation, the equation of water dissociation remains:

H 2 O ↔ H + + OH -

As you can see, there are no excess H + or OH - ions in the solution as compared to their content in water. In addition, no other weakly dissociating or sparingly soluble compounds are formed. Hence we conclude that salts formed by strong acids and bases do not undergo hydrolysis, and the reaction of solutions of these salts is the same as in water, neutral (pH \u003d 7).

When drawing up ion-molecular equations of hydrolysis reactions, it is necessary:

1) write down the equation of salt dissociation;

2) determine the nature of the cation and anion (find the cation of a weak base or anion of a weak acid);

3) write down the ionic-molecular equation of the reaction, taking into account that water is a weak electrolyte and that the sum of the charges must be the same in both sides of the equation.

Salts of weak acid and strong base

(Na 2 CO 3 , K 2 S, CH 3 COONa and dr .)

Consider the hydrolysis reaction of sodium acetate. This salt in solution decomposes into ions: CH 3 COONa ↔ CH 3 COO - + Na +;

Na + is a strong base cation, CH 3 COO - is a weak acid anion.

Na + cations cannot bind water ions, since NaOH - a strong base - completely decomposes into ions. Anions of weak acetic acid CH 3 COO - bind hydrogen ions to form low-dissociated acetic acid:

CH 3 COO - + HOH ↔ CH 3 COOH + OH -

It can be seen that as a result of the hydrolysis of CH 3 COONa, an excess of hydroxide ions was formed in the solution, and the reaction of the medium became alkaline (pH\u003e 7).

Thus, we can conclude that salts formed by a weak acid and a strong base are hydrolyzed at the anion ( An n - ). In this case, salt anions bind H ions + , and OH ions accumulate in the solution - , which determines an alkaline environment (pH\u003e 7):

An n - + HOH ↔ Han (n -1) - + OH - (at n \u003d 1, HAn is formed - a weak acid).

Hydrolysis of salts formed by dibasic and tribasic weak acids and strong bases proceeds stepwise

Consider the hydrolysis of potassium sulfide. K 2 S dissociates in solution:

K 2 S ↔ 2K + + S 2-;

K + is a strong base cation, S 2 is a weak acid anion.

Potassium cations do not take part in the hydrolysis reaction; only anions of weak hydrosulfuric acid interact with water. In this reaction, in the first stage, weakly dissociating HS - ions are formed, in the second stage, a weak acid H 2 S is formed:

1st stage: S 2- + HOH ↔ HS - + OH -;

2nd stage: HS - + HOH ↔ H 2 S + OH -.

OH - ions formed at the first stage of hydrolysis significantly reduce the probability of hydrolysis at the next stage. As a result, it is usually of practical importance that the process proceeds only in the first stage, which, as a rule, is limited when evaluating the hydrolysis of salts under normal conditions.

Chemical properties of oxides: basic, amphoteric, acidic

Oxides are complex substances consisting of two chemical elements, one of which is oxygen with an oxidation state ($ -2 $).

The general formula of oxides is $ E_ (m) O_n $, where $ m $ is the number of atoms of the element $ E $, and $ n $ is the number of oxygen atoms. Oxides can be solid (sand $ SiO_2 $, varieties of quartz), liquid (hydrogen oxide $ H_2O $), gaseous (carbon oxides: carbon dioxide $ CO_2 $ and carbon monoxide $ CO $ gases). According to their chemical properties, oxides are divided into salt-forming and non-salt-forming.

Non-salt-forming these are called oxides that do not interact with either alkalis or acids and do not form salts. There are few of them, they include non-metals.

Salt-forming these are called oxides that react with acids or bases and form salt and water.

Among the salt-forming oxides, oxides are distinguished basic, acidic, amphoteric.

Basic oxides - these are the oxides to which the bases correspond. For example: $ CaO $ is $ Ca (OH) _2, Na_2O is NaOH $.

Typical reactions of basic oxides:

1. Basic oxide + acid → salt + water (exchange reaction):

$ CaO + 2HNO_3 \u003d Ca (NO_3) _2 + H_2O $.

2. Basic oxide + acidic oxide → salt (compound reaction):

$ MgO + SiO_2 (→) ↖ (t) MgSiO_3 $.

3. Basic oxide + water → alkali (compound reaction):

$ K_2O + H_2O \u003d 2KOH $.

Acid oxides - these are oxides to which acids correspond. These are oxides of non-metals:

N2O5 corresponds to $ HNO_3, SO_3 - H_2SO_4, CO_2 - H_2CO_3, P_2O_5 - H_3PO_4 $, as well as metal oxides with high oxidation states: $ (Cr) ↖ (+6) O_3 $ corresponds to $ H_2CrO_4, (Mn_2) ↖ (+7 ) O_7 - HMnO_4 $.

Typical reactions of acidic oxides:

1. Acid oxide + base → salt + water (exchange reaction):

$ SO_2 + 2NaOH \u003d Na_2SO_3 + H_2O $.

2. Acid oxide + basic oxide → salt (compound reaction):

$ CaO + CO_2 \u003d CaCO_3 $.

3. Acid oxide + water → acid (compound reaction):

$ N_2O_5 + H_2O \u003d 2HNO_3 $.

This reaction is only possible if the acidic oxide is soluble in water.

Amphoteric oxides are called which, depending on the conditions, exhibit basic or acidic properties... These are $ ZnO, Al_2O_3, Cr_2O_3, V_2O_5 $. Amphoteric oxides do not combine directly with water.

Typical reactions of amphoteric oxides:

1. Amphoteric oxide + acid → salt + water (exchange reaction):

$ ZnO + 2HCl \u003d ZnCl_2 + H_2O $.

2. Amphoteric oxide + base → salt + water or complex compound:

$ Al_2O_3 + 2NaOH + 3H_2O (\u003d 2Na,) ↙ (\\ text "sodium tetrahydroxoaluminate") $

$ Al_2O_3 + 2NaOH \u003d (2NaAlO_2) ↙ (\\ text "sodium aluminate") + H_2O $.

Lesson topic: Creative tasks in GIA versions

Place of the lesson: generalizing lesson in grade 9 (in preparation for the GIA in chemistry).

Lesson duration: (60 min.).

Lesson content:

The lesson is structurally divided into 3 parts, corresponding to the questions in the GIA versions.

Obtaining gaseous substances. Qualitative reactions to gaseous substances (oxygen, hydrogen, carbon dioxide, ammonia) (A 14).

Determination of the nature of the medium of a solution of acids and alkalis using indicators. Qualitative reactions to ions in solution (chloride, sulfate, carbonate ions, ammonium ion) (A 14).

Chemical properties simple substances. Chemical properties of complex substances. Qualitative reactions to ions in solution (chloride, sulfate, carbonate ions, ammonium ion). Obtaining gaseous substances. Qualitative reactions to gaseous substances (oxygen, hydrogen, carbon dioxide) (C 3).

During the lesson, the teacher uses a multimedia presentation: "Creative tasks in the GIA versions", "Safety precautions in chemistry lessons", "Creative tasks in the GIA options" for the 3rd part of the lesson.

The purpose of the lesson: Prepare 9th grade students for the GIA in chemistry on specific issues. Purpose of work: to consolidate knowledge about properties inorganic compounds of different classes, about qualitative reactions to ions.Deepen students' knowledge of chemistry, develop interest in the subject.

Lesson Objectives :

- Deepen, systematize and consolidate,knowledge of students about the methods of obtaining, collecting and the properties of various gases;

Develop the ability to analyze, compare, generalize, establish cause-and-effect relationships;

To acquaint with the methodology for completing tasks of the GIA options on this topic;

To develop the skills and abilities of working with chemical reagents and chemical equipment;

Promote the development of skills to apply knowledge in specific situations;

Expand the horizons of students, increase motivation for learning, socialization of students through independent activities;

Help students get real experience in solving non-standard tasks;

Develop educational and communication skills;

To promote the development in children of the ability to exercise self-assessment and control of their activities;

Help students prepare for admission to secondary education.

Tasks for students:

Get acquainted with the implementation of creative tasks in the variants of the GIA (A-14, C3);

Learn to solve non-standard creative tasks;

Exercise control and self-control of their activities.

(Students read out).

Lesson type:

A lesson in improving knowledge, skills and abilities (a lesson in the formation of skills and abilities, the targeted use of what was learned in the GIA options)

a lesson in generalization and systematization of knowledge;

combined.

Forms of work:

Frontal, group, individual, collective.

Teaching methods and tools: independent work students, which they did at home, in the classroom, individual work, work in groups, laboratory experience, work at the blackboard, using ICT, handouts and objects of the abstract world.

Lesson effectiveness:

During the lesson, the teacher created conditions for the active activity of students, including creative.

Equipment: balloons, soap bubbles, individual cards, cards with tasks, assignments for practical work, cards with homework, a sheet with reflection, test "How did I learn the material?",computer, projector, screen, presentation. Tables: solubility, color of indicators, determination of ions. Tables at the blackboard.

Reagents: sodium carbonate, sodium chloride and sodium sulfate, hydrochloric acid, silver nitrate, barium chloride, calcium carbonate, water, ammonium chloride. Indicators: methyl orange, phenolphthalein, litmus).

Test "Our mood"

( Before the lesson, students are invited to take squares of any color that the children want to take):

Red - energetic (set to work).

Yellow is the color of joy, good mood.

Blue is the color of calm, poise.

Green is bored, but I hope this mood changes.

Brown - isolation.

Black is gloomy.

Lesson motto: Goethe's words: “It is not enough to know, you need to apply it.

It is not enough to want, you have to do it ”.

During the classes:

Warm up:

The founder of the theory of Electrolytic dissociation (Arrhenius).

The process of decomposition of the electrolyte into ions is called? (ED)

What substances are called electrolytes? (Substances, aqueous solutions or melts of which conduct electric current).

The positively charged ions are called (cations).

The negatively charged ions are called (anions).

Dissociation of alkalis produces ions (hydroxide ions).

List the conditions for the ion exchange reactions (ion exchange reactions go to the end in three cases: 1. As a result of the reaction, a precipitate is formed; 2. a low-dissociating substance or water; 3. a gaseous substance is formed) (students' answers).

When acids dissociate, ions (hydrogen ions) are formed.

First part of the lesson.

Obtaining gaseous substances. Qualitative reactions to gaseous substances (oxygen, hydrogen, carbon dioxide, ammonia)

You need to know:

Physical and chemical properties of gases (hydrogen, oxygen, carbon dioxide, ammonia).

Gas collection methods.

Name and operation of devices for obtaining gases

The main methods of obtaining gases in industry and laboratories

Gas identification ( qualitative reactions) .

1.Variety of gases. Distribute the gases you know into groups (individual work - students complete the assignment on separate sheets of paper, the answers are recorded on the screen, a mutual check is organized, the students are graded).

Formulas of gaseous substances are printed on sheets and pre-printed on the board:

O 2 , CO, H 2 , NO 2 , CO 2 , N 2 , NH 3 , H 2 S, CI 2 , HCI.

1) gases - simple substances;

2) gases - oxides;

3) colored gases;

4) gases with a characteristic odor;

Answer: 1) Simple substances: N 2 , O 2 , H 2 , Cl 2 .

2) Oxides: CO, CO 2 , NO 2 .

3) Colored gases: Cl 2 , NO 2 .

4) Gases with characteristic odor: Cl 2 , NO 2 , NH 3 , H 2 S, HCl.

2. Determine which gas the ball is filled with. To do this: Calculate the air density of the gases given to you.

On the board are suspended balloons of different colors, located at different heights. Within 5 minutes, students must determine which gas of those whose formulas are listed below, each balloon is filled: NH 3 , CO 2 , H 2 , ABOUT 2 .

We create groups. Each group receives its own gas (a ball of a different color, corresponding to the color of the cylinders in which the liquefied gas is transported. For example, oxygen: a ball - blue), the properties of which the group will determine. 1 group - H 2 , Group 2 - О 2 , Group 3 - CO 2 , Group 4 - NH 3 ... The students also answer: why are the balls at different heights?

3. Experience : Why do air bubbles go down? (Water gun). Children give the answer.

Group work:

4. Name physical properties gases given to you. Briefly. (Work in groups).

Oxygen-

Hydrogen -

Ammonia -

Carbon dioxide -

5. Answer the question: What methods of collecting gases do you know? Let's turn to the slide:

Devices for collecting gases.

2) What gases can be collecteddevice in Figure 1 and 2?

Lighter than air 1, heavier - 2.

3) What gases can be collected by the device in Figure 3?

Gases that are insoluble in water.

4) What device number will you collect

Group 1 - hydrogen? 2- oxygen?

ABOUT we are working on this issue on the instructions of the GIA:

A) ammonia B) oxygen

C) carbon dioxide D) hydrogen sulfide

Which gas is produced in the figure?

A) ammonia B) oxygen

C) carbon dioxide D) hydrogen

6 ... We will work out laboratory and industrial methods receiving gases on GIA issues: (according to the handout table 1.)

TO what gas do they get?

A) ammonia B) oxygen

C) carbon dioxide D) hydrogen

What gas do they get?

A) ammonia

B) oxygen

B) carbon dioxide

D) hydrogen

What gas do they get?

A) ammonia

B) oxygen

B) carbon dioxide

D) hydrogen

What gas do they get?

A) ammonia B) oxygen C) carbon dioxide D) hydrogen

What gas do they get?

A) ammonia B) oxygen

B) carbon dioxide D) hydrogen

7 .How to distinguish gases from each other?

What gas is determined?

A) ammonia B) oxygen

C) carbon dioxide D) hydrogen

What gas are the balls filled with?

A) hydrogen sulfide B) oxygen

C) carbon dioxide D) hydrogen

What gas is being poured over?

A) ammonia B) oxygen

C) carbon dioxide D) hydrogen

A distinctive feature of the 2012 A14 assignments was the questions on the pictures.

Thus, in the tasks of the GIA, the following questions on the drawings are encountered:

What gas is collected? (Collection methods)

What gas do they get? (Methods of obtaining)

What gas is determined? (Identification)

Presentation

2. The second part of the lesson.

Determination of the nature of the medium of a solution of acids and alkalis using indicators.

Qualitative reactions to ions in solution (chloride, sulfate, carbonate ions, ammonium ion.

Safety Rules (presentation).

1.Laboratory experience.

Safety in chemistry lessons (Multimedia presentation)

Determine the substances given to you in groups.

Group 1

HCI), alkalis (NaOH) and water (H 2 O). Using the substances dispensed (methyl orange), determine which tube each substance is in.

Group 2

Group 3

Appendix 1.2 (for group 1-3)

Practical work No. 1

Lesson objectives:

Equipment: board, chalk, table "Determination of the nature of the medium of a solution of acids and alkalis using indicators", "Table of solubility of acids, bases, salts in water", a rack with test tubes, an alcohol lamp, matches, a holder for test tubes.

Reagents: solutions: sodium hydroxide, hydrochloric acid, water, indicator - methyl orange.

Group 1

In three test tubes under the numbers there are solutions: acids (HCI), alkalis (NaOH) and water (H 2 O). Using the indicators issued by the substances (methyl orange, phenolphthalein, litmus), determine in which test tube each of the substances is located.

Instructions for work.

Assignment: in three numbered test tubes (1, 2, 3) substances are given: acids (HCI), alkalis (NaOH) and water (H 2 O).

Using characteristic reactions, recognize in which tube the given substances are located.

Perform experiments 1, 2, 3.

Pour 2 - 3 ml of solution into test tube # 1 and add 1 - 2 drops of methyl orange indicator solution, litmus, phenolphthalein, how did the color of the solution change?

Add a solution of methyl orange indicator, litmus, phenolphthalein to test tube No. 2.

What are you watching?

Add a solution of methyl orange indicator, litmus, phenolphthalein to test tube No. 3.

What are you watching?

3. Complete the table.

Make the necessary notes in the notebook, the conclusion is voiced (One student from the group speaks). See handout annex 1.2.

Color change

in an acidic environment

Color change in alkaline environment

Practical work No. 1

Topic: Qualitative reactions to ions.

Purpose of work: using characteristic reactions to recognize inorganic substances.

Improve the skills of conducting a chemical experiment;

In a practical way, confirm the conditions for carrying out ion exchange reactions.

Lesson objectives:

Educational: using a chemical experiment to consolidate the knowledge, skills and abilities of students in the section "Theory of electrolytic dissociation" (characteristic reactions to inorganic substances).

Developing: promote the development of thinking (analyze, compare, highlight the main thing, establish cause-and-effect relationships), the development of cognitive interests.

Educational: contribute to the formation of personality traits (responsibility, collectivism, initiative).

Lesson type: application of knowledge, skills and abilities in practice.

Lesson type: practical work.

Teaching methods: analytical, comparative, generalizing, classification.

Group 2

In three test tubes under the numbers there are solutions: sodium carbonate, sodium chloride and sodium sulfate. Using the substances given out (hydrochloric acid, silver nitrate, barium chloride), determine which tube contains each of the substances.

Instructions for work.

For this test, divide the contents of each numbered tube into three samples.

Working process:

1. A table for recording the performance of work in the form:

2. Perform experiments 1, 2, 3.

What are you watching?

What are you watching?

What are you watching?

Write the reaction equation in molecular, full ionic, abbreviated ionic forms.

3. Complete the table.

4. Make a general conclusion. Record the results of the experimental part of the work in the report table. Please use §§ 2,3,4 when preparing the report.

Make the necessary entries

Practical work No. 1

Topic: Qualitative reactions to ions.

Purpose of work: using characteristic reactions to recognize inorganic substances.

Improve the skills of conducting a chemical experiment;

In a practical way, confirm the conditions for carrying out ion exchange reactions.

Lesson objectives:

Educational: using a chemical experiment to consolidate the knowledge, skills and abilities of students in the section: "Theory of electrolytic dissociation" (characteristic reactions to inorganic substances).

Developing: promote the development of thinking (analyze, compare, highlight the main thing, establish cause-and-effect relationships), the development of cognitive interests.

Educational: contribute to the formation of personality traits (responsibility, collectivism, initiative).

Lesson type: application of knowledge, skills and abilities in practice.

Lesson type: practical work.

Teaching methods: analytical, comparative, generalizing, classification.

Equipment: blackboard, chalk, table of solubility of acids, bases, salts in water, a rack with test tubes, an alcohol lamp, matches, a holder for test tubes.

Reagents: solutions: hydrochloric acid, water, indicator - silver nitrate, calcium carbonate, sodium carbonate and sodium chloride, hydrochloric acid, ammonium chloride.

Group 3

Three test tubes with numbers contain solids: calcium carbonate, ammonium chloride and sodium chloride. Using the substances given out (hydrochloric acid, silver nitrate, sodium hydroxide), determine in which test tube each of the substances is located.

Instructions for work.

For this test, divide the contents of each numbered tube into three samples.

Working process:

1. Table for recording the performance of work in the form:

2. Perform experiments 1, 2, 3.

Pour the silver nitrate solution into test tube No. 1.

What are you watching?

Write the reaction equation in molecular, full ionic, abbreviated ionic forms.

Pour hydrochloric acid solution into test tube No. 2.

What are you watching?

Write the reaction equation in molecular, full ionic, abbreviated ionic forms.

Pour sodium hydroxide solution into test tube No. 3.

What are you watching?

Write the reaction equation in molecular, full ionic, abbreviated ionic forms.

3. Fill in the table.

4. Make a general conclusion. Record the results of the experimental part of the work in the report table. Please use §§ 2,3,4 when preparing the report.

Make the necessary entriesin a notebook, the conclusion is voiced. (One student per group speaking). See handout annex 1.2.

3.The third part of the lesson

Chemical properties of simple substances. Chemical properties of complex substances.

Qualitative reactions to ions in solution (chloride, sulfate, carbonate ions, ammonium ion).

Obtaining gaseous substances.

Qualitative reactions to gaseous substances (oxygen, hydrogen, carbon dioxide, ammonia)

Creative tasks, task C 3, tasks are difficult.

3. Each group is asked to solve one combined problem. The group decides together. The solution is recorded on the board

3.1 : Pavel Bazhov's fairy tale "The Mistress of the Copper Mountain" mentions a beautiful ornamental stone - malachite, from which vases, boxes, and jewelry are made. The chemical formula of malachite (CuOH) 2 CO 3 . Thermal decomposition of malachite produces three complex substances: one solid black and two gaseous. When one of the resulting gaseous substances is passed through lime water, its turbidity is observed due to the formation of sediment.

Write down chemical formula and the name of the resulting sediment. Write down the two molecular equations for the reactions that were performed.

Answer:t 0

(CuOH) 2 CO 3 → 2CuO + CO 2 + H 2 O

Malachite

CO 2 + Ca (OH) 2 → CaCO 3 ↓ + H 2 O

This reaction is used to detect carbon monoxide (IV).

3.2: Substance X 1 get the interaction of aluminum with a yellow powder. Under the action of water on X 1 poisonous gas with the smell of rotten eggs is released. This gas burns to form substance X 2 with a pungent smell. Determine X 1 their 2. Write down the equations of the reactions taking place. Indicate the molar mass of substance X 2.

Answer:

2Al + 3S → Al 2 S 3

Al 2 S 3 + 6 H 2 ABOUT → 3H 2 S + 2Al (OH) 3

2 H 2 S + 3 O 2 → 2 SO 2 + 2H 2 ABOUT

Al 2 S 3 - X 1 , SO 2 - X 2 M (SO 2 ) \u003d 64 g / mol

All experiments with hydrogen sulfide are carried out in a fume hood!

3.3: To determine the qualitative composition of the substance, the students were given a metal salt, 1 kg of which in 1854 cost 270 times more than silver, and in the middleXX century has already been widely used for the manufacture of light metal structures. After dissolving the crystals of the given salt in water, the schoolchildren poured the resulting clear solution into two test tubes.

A few drops of sodium hydroxide solution were added to one of them, and a gel-like white precipitate was formed. A few drops of barium chloride solution were added to another tube containing the salt solution, and a white, milk-like precipitate formed.

Write down the chemical formula and the name of the given salt. Make two equations of the reactions that were carried out in the process of recognizing it.

Answer:

Al 2 (SO 4 ) 3 + 6NaOH → 3Na 2 SO 4 + 2Al (OH) 3 ↓ gelatinouswhitesediment

Al 2 ( SO 4 ) 3 + 3 BaCl 2 → 3 BaSO 4 ↓+ 2 AlCl 3

white milk-like sediment

Summing up the lesson. Reflection. Grading.

Evaluation-reflective block

Let's analyze your work in groups. The floor is given to the head of each group.

What questions did we discuss in the lesson today?

Which of these questions did you find the most difficult?

Test Appendix 3

How did I learn the material?

Homework (assignment printed to each student)

Problem number 1.

For the experiments, the researchers were given a substance in the form of water-insoluble yellow crystals. It is known to be used in the manufacture of matches and in the vulcanization of rubber. As a result of the interaction of the dispensed substance with concentrated sulfuric acid, a gaseous oxide and water are formed upon heating. And when the formed oxide is passed through a solution of barium hydroxide, a white precipitate is formed, which dissolves upon further passing the gas.

Write down the chemical formula and name the salt obtained as a result of the second experiment. Write two molecular reaction equations that correspond to the student's experiments on salt.

t 0

S + 2H 2 SO 4 \u003d 3SO 2 + 2H 2 O

SO 2 + Ba (OH) 2 \u003d BaSO 4 ↓ + 2H 2 O

Barium sulphate

(At the end of the lesson, students who want to change the square to a square of a different color are invited to do so. Test "Our mood").

Attachment 1.

Table. Determination of ions

Reaction result

H +

Indicators

Color change

Ag +

Cl -

White sediment

WITHu 2+

OH -

S 2-

Blue sediment

Black sediment

Coloring the flame blue-green

Fe 2+

OH -

Greenish sediment that turns brown over time

Fe 3+

OH -

Brown precipitate

Zn 2+

OH -

S 2-

White precipitate, in excessOH - dissolves

White sediment

Al 3+

OH -

White, jelly-like precipitate, which in excessOH - dissolves

NH 4 +

OH -

Ammonia smell

Ba 2+

SO 4 2-

White sediment

Flame coloring in yellow-green color

Ca 2+

CO 3 2-

White sediment

Flame staining brick red

Na +

Flame color yellow

K +

Flame color purple (through cobalt glass)

Cl -

Ag +

White sediment

H 2 SO 4 *

Emission of a colorless gas with a pungent odor (HCl)

Br -

Ag +

H 2 SO 4 *

Yellowish precipitate

HighlightingSO 2 andBr 2 (brown)

I -

Ag +

H 2 SO 4 +

Yellow sediment

HighlightingH 2 S andI 2 (purple)

SO 3 2-

H +

HighlightingSO 2 - a gas with a pungent odor, decolorizing a solution of fuchsin and purple ink

CO 3 2-

H +

Evaporation of odorless gas causing cloudy lime water

CH 3 COO -

H 2 SO 4

Odor of acetic acid

NO 3 -

H 2 SO 4 (conc.) andCu

Separation of brown gas

SO 4 2-

Ba 2+

White sediment

PO 4 3-

Ag +

Yellow sediment

OH -

Indicators

Changing the color of indicators

Appendix 2.

Practical work No. 1

Topic: Qualitative reactions to ions.

Purpose of work: using characteristic reactions to recognize inorganic substances.

Improve the skills of conducting a chemical experiment;

In a practical way, confirm the conditions for carrying out ion exchange reactions.

Lesson objectives:

Educational: using a chemical experiment to consolidate the knowledge, skills and abilities of students in the section "Theory of electrolytic dissociation" (characteristic reactions to inorganic substances).

Developing: promote the development of thinking (analyze, compare, highlight the main thing, establish cause-and-effect relationships), the development of cognitive interests.

Educational: contribute to the formation of personality traits (responsibility, collectivism, initiative).

Lesson type: application of knowledge, skills and abilities in practice.

Lesson type: practical work.

Teaching methods: analytical, comparative, generalizing, classification.

Equipment: blackboard, chalk, table of solubility of acids, bases, salts in water, a rack with test tubes, an alcohol lamp, matches, a holder for test tubes.

Reagents: sodium carbonate, sodium chloride and sodium sulfate, hydrochloric acid, silver nitrate, barium chloride.

Group 2

In three test tubes under the numbers there are solutions: sodium carbonate, sodium chloride and sodium sulfate. Using the substances given out (hydrochloric acid, silver nitrate, barium chloride), determine which tube contains each of the substances.

Instructions for work.

For this test, divide the contents of each numbered tube into three samples.

Working process:

1. A table for recording the performance of work in the form:

2. Perform experiments 1, 2, 3.

Pour barium chloride solution into test tube No. 1.

What are you watching?

Write the reaction equation in molecular, full ionic, abbreviated ionic forms

Pour hydrochloric acid solution into test tube No. 2.

What are you watching?

Write the reaction equation in molecular, full ionic, abbreviated ionic forms.

Pour silver nitrate solution into test tube No. 3.

What are you watching?

Write the reaction equation in molecular, full ionic, abbreviated ionic forms.

3. Complete the table.

4. Make a general conclusion. Record the results of the experimental part of the work in the report table. Please use §§ 2,3,4 when preparing the report.

Make the necessary entries in a notebook, the conclusion is voiced. (One student per group speaking).

Appendix 3

Test

How did I learn the material?

1. Got solid knowledge, mastered all the material 9-10 points

2. Partially mastered the material 7-8 points

3. I understood a little, I still need to work 4-6 points

4. How would you rate yourself for participating in groups? (Rate yourself here).