Page 4
b) Sulfuric acid was poured into a test tube, a solution of potassium permanganate KMnO4 was added. The resulting mixture was divided equally among three test tubes. A piece of granulated zinc was dropped into each tube. Several KNO3 crystals were added to the first test tube, 2-3 times more potassium nitrate was added to the second, and the third was left for comparison.
The most rapidly discoloration of the solution occurred in the second test tube, in the first one the discoloration was slower, in the third - the discoloration was hardly noticeable. The release of gas bubbles occurred in a similar way.
2KMnO4 + 3H2SO4 + 2Zn → ZnSO4 + K2SO4 + MnSO4 + 3H2
Conclusion: MnO2 is a catalyst in the decomposition of hydrogen peroxide. KNO3 is a catalyst in the interaction of zinc, sulfuric acid and potassium permanganate.
Experience 5. Homogeneous catalysis. In the previous experiment, the hydrogen peroxide decomposition reaction was accelerated by a heterogeneous catalyst - solid manganese oxide MnO2.
H2O2 → H2O + ½O2.
This reaction is also accelerated with the help of a homogeneous catalyst - a complex ion - copper tetraammonate 2+. This catalyst is complex, so it is necessary to study the effect of its constituent components - copper ion and ammonia. For this purpose, 2 ml of a CuSO4 solution and 0.5 ml of H2O2 should be poured into one test tube, and 2 ml of an aqueous ammonia solution and 0.5 ml of H2O2 should be poured into the second. In both test tubes, the formation of small oxygen bubbles is observed as a result of the weak catalytic action of the components that make up the complex compound.
Pour 2 ml of a CuSO4 solution into the third test tube and add an aqueous ammonia solution until a dark blue complex compound appears:
CuSO4 + 4NH3∙H2O → 4H2O + SO4.
Add 2 ml of 3% H2O2 to the resulting catalyst solution. It is in the third test tube that the most intense gas evolution will be observed. It can be seen that the catalyst is not consumed during the reaction, but only accelerates the course of the process.
Conclusion: SO4 is also a catalyst in the decomposition of hydrogen peroxide.
Experience 6. Shift of chemical equilibrium in a homogeneous system.
The influence of the concentration of starting substances and reaction products on the chemical equilibrium in a homogeneous system can be studied using the reaction as an example:
FeCl3 + 3NH4CNS ↔ Fe(CNS)3 + 3NH4Cl.
Mix in a test tube a few milliliters of iron (III) chloride and ammonium cyanide.
As a result, the contents of the tube turn dark red. The resulting mixture was divided into 4 tubes.
In the first, 2-3 drops of ammonium thiocyanate were added. A little concentrated solution of iron chloride (III) was poured into the second. A little crystalline ammonium chloride was poured into the third and shaken vigorously. Color changes are noted in Table 3.
In the first test tube, vpr > vrev, in the second - vpr = vrev, in the third - vpr< vобр.
By the reaction with the addition of NH4CNS, iron thiocyanate is formed, which leads to an increase in its concentration and darkening of the solution; by the reaction with the addition of NH4Cl (solid), iron thiocyanate is consumed, which leads to a decrease in its concentration and clarification of the solution.
NH4CNS shifts the equilibrium in the direction of the forward reaction, and NH4Cl (solid) in the direction of the reverse.
Expression for the chemical equilibrium constant:
Conclusion: the addition of ammonium cyanide shifts the chemical equilibrium towards the forward reaction, solid ammonium chloride - towards the reverse reaction, iron (III) chloride does not affect the chemical equilibrium.
Experience 7. Effect of temperature on chemical equilibrium
2 ml of ammonia solution was poured into a test tube and 2 drops of phenolphthalein were added. The test tube was heated. As a result of the change in temperature, the solution brightened. Due to the increase in temperature, part of the ammonia solution evaporated, therefore, its concentration decreased. Heating shifted the equilibrium in the direction of the reverse reaction.
Introduction
One eccentric from the party of geologists Said to me, pouring mud from his boot ...
Seventh group of the periodic system
Of the members of this group, hydrogen has been considered previously. The elements immediately following it - F, Cl, Br and I - are collectively called halogens. They should also include...
Appendix 6
Treatment of oil, including gas condensate, tons Russian Federation 910610930 Western Siberia 708316453 Tyumen region...
but) heterogeneous catalysis. Pour ¼ volume of hydrogen peroxide into three test tubes. Simultaneously add: manganese (II) oxide (MnO 2) to the first test tube, silicon (IV) oxide (SiO 2) to the second, iron (II) oxide (FeO) to the third. Observe the decomposition reaction of hydrogen peroxide. The release of oxygen can be determined by dropping a smoldering splinter into a test tube. Is the reaction equally fast in test tubes? Which substance is not a catalyst for a decomposition reaction? Write down the reaction equation.
b) homogeneous catalysis. Pour a 0.5M solution of sulfuric acid into two test tubes for 1/3 of the volume. Drop a piece of zinc into each test tube and add 5 drops of potassium permanganate solution (KMnO 4). Leave one test tube as a reference, and add a few crystals of potassium nitrate (KNO 3) as a catalyst to the other. In which of the test tubes does the solution decolorize faster? Record the overall reaction.
When metal zinc interacts with a solution of sulfuric acid, atomic hydrogen is formed, which, recombining, is released in the form of H 2 gas. In the first tube, the reduction of potassium permanganate occurs directly with atomic hydrogen (the reaction proceeds rather slowly). In the second tube, atomic hydrogen first reduces the NO 3 - ion to the NO 2 - ion, which reacts with potassium permanganate much faster.
In this case, the MnO 4 - ion is reduced to Mn 2+, and the NO 2 - ion is again oxidized to NO 3 - .
1) Zn + H 2 SO 4 \u003d ZnSO 4 + 2H
2) 2H = H 2 - recombination
3) 5KNO 3 + 10H = 5KNO 2 + 5H 2 O
4) 5KNO 2 + 2KMnO 4 + 3H 2 SO 4 = 5KNO 3 + 2MnSO 4 + K 2 SO 4 + 3H 2 O
Thus, potassium nitrate, participating in the intermediate stages of the process, contributes to a more rapid course of the reduction reaction of potassium permanganate. KNO 3 itself is not consumed as a result of the reaction and remains in the originally taken amount.
Experience 4. Chemical equilibrium and its displacement
but) Effect of concentration change on equilibrium shift. A classic example of a reversible reaction is the interaction between iron(III) chloride and potassium thiocyanate. The solution of iron thiocyanate Fe(CNS) 3 formed as a result of the reaction has a red color, the intensity of which depends on its concentration. Equilibrium shift is easy to observe by changing the color of solutions.
Pour into a 50 ml glass ¾ of the volume of distilled water and add 2 drops of saturated solutions of FeCl 3 and KCNS. Pour the red-colored solution equally into 4 test tubes. Compose a reaction equation and write down the expression for the chemical equilibrium constant (K s).
Leave the first tube as a reference, add 2 drops of a saturated solution of FeCl 3 to the second, 2 drops of a saturated solution of KCNS to the third, and add a few crystals of KCl to the fourth. Compare the colors of the resulting solutions and explain the shift in equilibrium.
b) in solutions of chromium salts (chromate and dichromate) there is an equilibrium 2CrO 4 2- + 2H + ⇄ Cr 2 O 7 2- + H 2 O.
solution of ions Cr 2 O 7 2- - orange. A change in the concentration of hydrogen ions H + shifts this equilibrium in one direction or another.
In a glass with a capacity of 50 ml, pour a solution of potassium chromate (K 2 CrO 4) into 1/5 of the volume. To this solution, add concentrated sulfuric acid drop by drop and observe the color change. Then add a solution of concentrated alkali (NaOH) dropwise to the resulting solution and again observe the appearance of the original color.
Write the complete reaction equation. Draw a conclusion in which medium (pH) chromate and dichromate ions exist.
in) Effect of Temperature on Chemical Equilibrium. IN
pour 1M ammonia solution (NH 4 OH) into a test tube for 1/2 volume. Add 1 drop of phenolphthalein and observe the appearance of a crimson color. Heat the test tube over a burner flame. The coloring disappears. When the solution is cooled, the crimson color reappears. Make a conclusion about the effect of temperature on the shift in equilibrium.
HOMEWORK OPTIONS
| var. no. | task number | var. no. | task number |
| 1a, 17, 25a, 34, 58 | 1l, 24g, 25l, 47, 67(d, f) | ||
| 1b, 18, 25b, 36, 59 | 1m, 24d, 25m, 48, 67(w,w) | ||
| 1v, 19, 25v, 37, 60 | 1n, 24e, 25n, 51, 67(i, j) | ||
| 1g, 20, 25g, 39, 61 | 1o, 24g, 25o, 52, 67(l,m) | ||
| 1d, 21, 25d, 40, 62(а,b,c) | 1p, 24z, 25p, 53, 67(n, o) | ||
| 1f, 22, 25f, 41, 62(d,e,f) | 1p, 24i, 25p, 55, 68(a,b) | ||
| 1g, 23, 25g, 43, 63(a,b) | 1s, 9, 25s, 56, 68(c, d) | ||
| 1h, 24a, 25h, 44, 63(c,d) | 1t, 10, 25t, 42, 67(o,p) | ||
| 1i, 24b, 25i, 45, 67(a,b) | 1y, 3, 26, 49, 64(а,b) | ||
| 1k, 24v, 25k, 46, 67(c, d) | 1f, 6, 27, 50, 64(c, d) |
Lab #1
1. Properties of soluble and insoluble bases. Consider the hydroxides of sodium, calcium, copper (II) and iron (III) given to you in test tubes, note their state of aggregation and color. Pour 3-4 ml of water into test tubes and shake. Filter cloudy liquids. Add a few drops of phenolphthalein solution to the solutions. Sodium hydroxide is soluble in water, calcium hydroxide is partially soluble, and copper (II) and iron (III) hydroxides practically do not dissolve in water. Solutions of sodium hydroxide and calcium hydroxide stain phenolphthalein crimson. Filtered liquids, in which copper (II) and iron (III) hydroxide was agitated, do not affect the phenolphthalein solution.
The task. Based on the experiments carried out, draw a conclusion about the solubility of the bases.
2. Action of acids on metals. Place two pieces of zinc into two test tubes, pour a little iron powder into the other two, and copper shavings into the last two. Pour 1 ml of sulfuric acid into one test tube with zinc, and the same amount of hydrochloric acid into another. Zinc reacts vigorously with acids. This releases a gas that can burn. In the same way, pour the acids into the test tubes with iron and copper. Iron reacts with acids more slowly than zinc: copper at ordinary temperatures does not react with either sulfuric or hydrochloric acids. When heated, copper reacts with concentrated sulfuric acid. In this reaction, a colorless gas with a pungent odor is released (smell carefully!) and a blue solution is formed in the test tube.
Tasks. 1. Find iron, zinc and copper in N.N. Beketov's series and think about what properties this series is based on. 2. Write the equations for the chemical reactions that were observed in this experiment. What type of reactions are these?
3. Interaction of acids with basic oxides. An experience. Pour a little copper oxide (II) into two test tubes. Pour 1 ml of dilute hydrochloric acid into one of them, and the same amount of dilute sulfuric acid into the other. Heat the test tubes slightly. When heated in test tubes with copper (II) oxide, the solution acquires a blue color.
Pour a few drops of the solution from each tube onto a glass plate, evaporate it and see what is left on the plate. After evaporation of the solution, crystals are separated on the glass plate.
Tasks. 1. What are the signs that basic oxides react with acids? 2. What substances were released on glass plates after the solutions were evaporated? Write the chemical formulas of these substances. 3. Make the equations of the reactions that took place in these experiments.
4. Action of acids on indicators. Place nine test tubes in a rack. Pour 1 ml of dilute sulfuric acid into the first three test tubes, 1 ml of dilute hydrochloric acid into the second three, and the same amount of dilute nitric acid into the remaining three. In the first test tube with sulfuric acid, add a few drops of purple litmus solution or drop purple litmus paper, pour a few drops of phenolphthalein solution into the second test tube, and methyl orange into the third. Carry out the same experiments with hydrochloric and nitric acids.
Acids turn litmus red, phenolphthalein remains colorless, and methyl orange turns pink.
The task. Several solutions are given. How can one practically prove that one of them is an acid solution and the other is an alkali solution?
5. Interaction of acids with alkalis (neutralization reaction). Pour 1 ml of sodium hydroxide solution into a test tube and add a few drops of phenolphthalein solution to it. Using a pipette, add hydrochloric acid drop by drop to the crimson solution. Shake the vial after each drop. There is a heating and discoloration of the solution. Then transfer some of the resulting solution to a glass plate and evaporate it. White crystals stand out.
Tasks. 1. Consider why the acid solution should be added carefully, drop by drop. 2. What substance was released during the evaporation of the solution? Write its chemical formula. 3. Write an equation for the reaction between hydrochloric acid and sodium hydroxide. What type of reaction is this?
6. Interaction of acids with insoluble bases. Get some copper(II) hydroxide. To do this, pour 1 ml of sodium hydroxide solution into two test tubes and add the same amount of copper (II) sulfate solution or another soluble copper salt. Add hydrochloric acid to one test tube with the resulting precipitate until complete dissolution, and sulfuric acid to the other. A blue solution forms in both test tubes. Transfer a few drops of the resulting solutions to a glass plate and evaporate. Blue crystals stand out.
Tasks. 1. Write the chemical formulas of substances whose crystals stand out on glass plates. 2. Write the equations for the reactions that were observed in this experiment.
7. Interaction of acid oxides with water and alkalis. Experience I. Pour approximately 5 ml of water into a test tube, add 1-2 drops of phenolphthalein solution, and then dilute sodium hydroxide solution until a faint color appears. Pass excess carbon monoxide (IV) through the solution. Discoloration occurs.
Experience 2. Pour 2-3 ml of freshly prepared lime water into a test tube and pass carbon monoxide (IV) through it until the solution becomes cloudy.
Tasks. 1. Explain why the discoloration of the solution occurred in the first experiment. Write an equation for the corresponding reaction. 2. Why did the solution become cloudy in the second experiment? Write the reaction equation.
8. Obtaining and properties of zinc hydroxide. Pour 1 ml of a solution containing 0.05 mass fractions, or 5%, of sodium hydroxide into two test tubes, and then add a solution of zinc sulfate until a precipitate forms. Add excess sodium hydroxide to one test tube with sediment and shake. Pour sulfuric or hydrochloric acid into another test tube. For comparison, get iron (III) hydroxide in two test tubes. Add acid to the sediment in the first test tube, and an excess of alkali to the sediment in the second.
The precipitate of zinc hydroxide reacts with both acids and alkalis, iron (III) hydroxide reacts only with acids.
Tasks. 1. Write two equations of chemical reactions with which you can get: a) zinc hydroxide; b) iron (III) hydroxide. 2. Write the reaction equations for the interaction of zinc hydroxide: a) with hydrochloric acid; b) with sodium hydroxide. What are these hydroxides called?
| | | next lecture ==> | |
>> Chemistry: Properties of electrolytes (chemical workshop)
Practical work number 8. Ionic reactions
Experience 1.
Sulfate Ion Detection
Pour the sodium sulfate solution into a test tube, and the potassium sulfate solution into another. Add barium chloride solution dropwise to both tubes. Explain what you see. Make an equation for the electrolytic dissociation of the salts taken and an equation for the exchange reaction. Write down the equation for the reaction. Which compounds can serve as a reagent for barium ions Ba 2 +. What is the essence of detecting ions using a reagent?
Experience 2
Detection of chloride ions VI
According to the solubility table, find out which salts containing the chloride ion Cl are insoluble. Using the reagents you have, prove that chloride ions are present in the sodium chloride solution. Make an equation for the dissociation of salts, exchange reactions and an ionic equation for the reactions carried out.
Experience 3.
Detection of sulfate ions SO 2- 4 and chloride ions Cl -
Two test tubes contain solutions of potassium chloride and magnesium sulfate. What reactions can be used to prove that one test tube contains a solution of potassium chloride, and the other contains a solution of magnesium sulfate?
Divide the solution from the first test tube in half and pour into two test tubes. Pour a solution of lead (II) nitrate into one, and a solution of barium chloride into the other. In which test tubes did the precipitate fall out? Which of the salts is contained in the first test tube?
Test the second tube solution for the presence of an anion not found in the first tube. To do this, add a solution of lead nitrate (II) to the test solution.
Explain what you see.
Write the equations for the reactions of the exchange of the reactions you have carried out and the ion equations for the reactions of detecting ions.
Experience 4.
Perform reactions confirming the qualitative composition of the following substances: a) barium chloride; b) magnesium sulfate; c) ammonium carbonate. Use Table 12 to complete this experiment.
Practical work number 9. Conditions for the flow of chemical reactions between electrolyte solutions to the end
Experience 1.
Take three test tubes. Pour 2-3 ml of the solution into each: copper (II) sulfate in the first, potassium chloride in the second, aluminum sulfate in the third. Then add to each tube: in the first a little sodium hydroxide solution, in the second - sodium phosphate, and in the third - barium chloride. What are you watching? Write molecular and ionic reaction equations. Make a conclusion.
Experience 2.
Pour 2-3 ml of sodium sulfite and sodium carbonate solutions into two test tubes, respectively. Then pour a solution of nitric acid into each of them. What are you watching? Write molecular and ionic reaction equations. Make a conclusion.
Experience 3.
Pour 3-4 ml of sodium hydroxide solution into one test tube and add two to three drops of phenolphthalein. The solution takes on a crimson color. Then add a solution of hydrochloric or sulfuric acid until discoloration.
Pour about 10 ml of copper (II) sulfate into another test tube and add a little sodium hydroxide solution. A blue precipitate of copper(II) hydroxide is formed. Pour sulfuric acid into the test tube until the precipitate dissolves.
Make up the equations of the ongoing reactions in molecular and ionic form. Explain why discoloration occurred in the first test tube, and dissolution of the precipitate in the second. What property do soluble and insoluble bases have in common?
Practical work number 10. Properties of acids, bases, oxides and salts
Exercise 1.
Write reactions that characterize the properties of solutions:
a) hydrochloric acid (1 option);
b) sulfuric acid (2nd option).
Write down the equations of the reactions you have done in molecular and ionic forms. Consider the reaction with the metal as a redox reaction.
Task 2.
Perform reactions characterizing the properties of sodium hydroxide solution (I option).
Get iron (III) hydroxide by an exchange reaction and carry out reactions that characterize its chemical properties (option 2).
Write down the equations of the reactions we have done in molecular and iozzo forms.
Task 3.
Get sulfur oxide (IV) and perform reactions characterizing its properties (I option).
Perform reactions that characterize the properties of calcium oxide (option 2).
Write down the reaction equations in molecular and ionic form, if possible.
Task 4.
Perform reactions that characterize the properties:
a) iron chloride (II) (option 1);
b) copper (II) chloride (option 2).
Write down the reaction equations in molecular and ionic forms. Consider reactions involving metal as redox reactions.
Practical work 11. Solution of experimental problems
1. Pour 1-2 ml of a concentrated sulfuric acid solution into a test tube and dip a piece of zinc into it. Write a reaction equation in molecular, ionic and abbreviated ionic form, show the transition of electrons. What is the oxidizing agent in this reaction?
2. In six test tubes there are solutions of chloride machines. Pour the following solutions into each of the test tubes: a) sodium hydroxide; b) potassium sulfate; c) sodium carbonate; d) zinc nitrate; e) potassium phosphate; e) sodium sulfide.
Make up the equations of the reactions proceeding to the end, in molecular, ionic and abbreviated ionic form.
3. Solutions are given:
a) potassium carbonate and hydrochloric acid;
b) sodium sulfide and sulfuric acid;
c) zinc chloride and nitric acid;
d) sodium sulfite and sulfuric acid;
e) copper sulfate (II) and nitric acid.
Pour off these solutions in pairs, heat a little and carefully determine by smell in which cases the reactions proceed to the end and why. Write the equations for the corresponding reactions in molecular, ionic, and abbreviated ionic form.
4. Carry out the reactions, the schemes of which are given:
5. Perform reactions between the following substances: a) hydrogen sulfide and chlorine water; b) a solution of potassium iodide and chlorine water; c> hydrochloric acid and aluminum; d) concentrated sulfuric acid and copper (when heated).
Make the reaction equations, show the transition of electrons. What is an oxidizing agent and what is a reducing agent?
6. Using the solutions on the table, get: a) iron hydroxide (ІІІ); b) copper (II) sulfide; c) sulfur oxide (IV); d) magnesium carbonate; e) lead.
Write molecular, ionic, and abbreviated ionic equations for the corresponding reactions.
This methodological development presents practical work on the topic "Ion exchange reactions", carried out according to the instructions. Such a lesson can be carried out when studying the topic "Theory of electrolytic dissociation." In order to increase the effectiveness of the lesson, to make practical work more interesting, it is proposed to use game moments in the course of the lesson.
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Methodical development
FEDERAL STATE INSTITUTION
SECONDARY VOCATIONAL EDUCATION
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Methodical development
chemistry lesson on the topic "Ion exchange reactions"
to help teachers
Full-time departments of specialties2901 "Architecture"
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Compiled by Demyanenko A.A.
Introduction 4
1. Preparing for Lesson 6
2. Structure and content of lesson 9
3. Conclusion 12
4. List of used literature 13
Appendix 14
Introduction
A student experiment is a type of independent work. The chemistry program stipulates which experimental work must be carried out.
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 polytechnics, since the main essence of this principle is the connection with life, with the future practical activities of students.
The student experiment is divided into laboratory experiments and practical exercises. They differ in didactic purpose. The purpose of laboratory experiments is the acquisition of new knowledge, the study of new material. Practical classes are usually held at the end of the study of the topic and serve to consolidate and improve, concretize knowledge, form practical skills, improve existing skills and abilities of students.
The implementation of a student experiment from the point of view of the learning process should go through the following stages: 1) understanding the purpose of the experiment; 2) the study of substances; 3) assembly or use of a new device; 4) performance of experience; 5) analysis of results and conclusions; 6) explanation of the obtained results and compilation of chemical equations; 7) drawing up a report.
The student must understand why he is doing the experiment and what he must do to solve the problem posed to him. He studies substances organoleptically or with the help of devices or indicators, examines the details of the device or the device itself. The implementation of the experiment requires mastery of techniques and manipulations, the ability to observe and notice the features of the course of the process, to distinguish important changes from insignificant ones. After analyzing the work, which the student must do on his own, he draws a conclusion based on the relevant theoretical concept. Do not underestimate the role of the report that students make immediately after the experiment. He teaches concise and precise formulation of thought, correct recording.
The selection of a system of adequate methods and means of teaching is a creative process. In order to increase the effectiveness of the lesson, it is necessary to select a system of teaching methods based on specific conditions, to be well versed in the methodological literature, in the complex of teaching and upbringing tools.
This methodological development presents practical work on the topic "Ion exchange reactions", carried out according to the instructions. Such a lesson can be carried out when studying the topic "Theory of electrolytic dissociation." In order to increase the effectiveness of the lesson, to make practical work more interesting, it is proposed to use game moments in the course of the lesson.
1. Preparing for the lesson.
Reagents and equipment
Each student, or in pairs, before the start of the lesson, is given the following set:
- Reagents: solutions of copper sulfate, sodium hydroxide, aluminum sulfate, barium nitrate, sodium carbonate, hydrochloric acid, sulfuric acid, phenolphthalein.
- Equipment: four test tubes, pipette.
2. Structure and content of the lesson
Topic: Ion exchange reactions
Lesson Objectives: to deepen the concept of the properties of electrolytes as the properties of ions; repeat and consolidate in practice information about ionic reactions, neutralization reactions; improve the skills of compiling full and reduced ionic reaction equations.
The lesson is held after studying the topic "Theory of electrolytic dissociation", when students already know the terminology, are familiar with scientific facts and theory on this topic, have an idea about ion exchange reactions, and are able to compose complete and reduced ionic equations.
Before the lesson, several students are invited to write a short story, story or fairy tale on the topic “Ion Exchange Reactions”, so that the actors are ions, substances (acids, bases, salts), etc.
In advance, you need to prepare a bright crossword on whatman paper.
Guys, in the previous few lessons we studied the Theory of Electrolytic Dissociation. In today's lesson, we will continue to do practical work on this topic. I propose to conduct our lesson in the form of an oral journal.
? which means α=0.8 and α=0.2
? What is wrong with Vanya?
Vanya and hydrolysis
For example, the water of the seas is a solution of salts.
- anions "run" to it
? How is the anode charged?
? name the term that is opposite in meaning (antonym);
- hydrochloric, phosphoric, nitrogen ...
- hydroxides in a different way
- if there is a precipitate
- if gas is formed
If gas is released - this is the time;
And you get water - these are two;
“There is sediment” - we say.
This is the third important point.
gas or water
Precipitation falls - then - order!
Practical work No. 13
Topic:
Experience #1:
Experience #2:
Experience #3:
In the course of the work, I propose to play the game "Tic-tac-toe". Rules of the game:
- We will be divided into two teams - "crosses" and "tac-toes"
- The playing field is prepared on the board in advance:
A B C
3
- After each experiment, I will ask a question.
- The first person to give the correct answer gets the turn. If it was a member of the "Cross" team, then in the cell chosen by him, for example 2b, I put the sign "x" (if a member of the other team answered, then "o").
- The result of each round is estimated by one point. The total result is the sum of points for each round.
- The most active members of the winning team will receive "5", the losing team - "4".
Questions.
Experience #1:
- Write the molecular equation for the reaction on the board.
- Write the full ionic equation for the reaction on the board.
- Write the equation for the reaction in abbreviated ionic form on the board.
Experience #2:
- Write the molecular equation for the reaction on the board.
Experience #3:
- Write the molecular equation for the reaction on the board.
Fairy tale "Magic Elixir", author Volotskaya Anastasia.
Answer: alkali; FeCl 3 + MeOH \u003d Fe (OH) 3 ↓ + MeCl 3
Story "Accident in Substance", author Budycheva Katrin.
3 + 3NaOH = Al(OH) 3 ↓ + 3NaCl)
3 3 + NaOH \u003d Na (Al (OH) 4 )) sodium aluminate hydrate)
Think of a more convenient way to get Al(OH)3. (Answer:
- From soda Na 2 CO 3:
3Na 2 CO 3 + 2 AlCl 3 + 3H 2 O \u003d 2Al (OH) 3 ↓ + 6 NaCl + CO 2
- From salts with ammonia:
Al 2 (SO 4) 3 + 6NH 3 + 6H 2 O \u003d 2Al (OH) 3 ↓ + 3 (NH 4) 2 SO 4
Fairy tale " ”, author Reshetnikova Olga
Dictation.
- dissociation -
- anode -
- cation -
- oxidizer -
- acid properties -
- starting materials -
- metal -
- electron donor -
Grading a lesson.
- Conclusion
In developing this lesson, the following goals were set:
- didactic: deepen the concept of the properties of electrolytes as the properties of ions, repeat and consolidate information about ionic reactions, neutralization reactions;
- developing: development of mental operations (analysis, synthesis), creative imagination, memory;
- educational: education of personal perception of the surrounding chemical processes (in chemical industries, ion exchange in aquatic environments, air ionization, etc.)
The set goals are achieved using verbal-visual and practical methods. The technique of conducting a practical lesson using game elements of educational activity is shown, which increases the interest of students in the subject, activates their cognitive activity.
- List of used literature
- From the experience of teaching inorganic chemistry in high school: Book. For the teacher/Comp. Surovtseva R.P.. - M .: Education, 1985.
- Rudzitis G.E., Feldman F.G. Chemistry. - M.: Enlightenment, 1986.
- Volovich P.M., Brovko M.I. Getting ready for the chemistry exam. – M.: Rolf; Iris-press, 1998.
- Chernobelskaya G.M. Fundamentals of methods of teaching chemistry: Proc. Allowance for students ped. in-comrade - M .: Education, 1987.
- Zueva M.V., Ivanova B.V. Improving the organization of educational activities in chemistry lessons. - M .: Education, 1989.
- Malyshkina V. Entertaining chemistry. St. Petersburg, "Trigon", 2001.
- 111 questions in chemistry ... for everyone: Book. for students / Benesh P., Pumpr V., Svobodova M., Mansurov G. - M .: Education, 1994.
☺ We open its first page - theoretical. Let's start our lesson by repeating the basic concepts, terms that we encountered while studying this theory. I propose to do this by solving a crossword puzzle.
- to describe quantitative relations in this process, a characteristic is used, denoted by the letter α
? define this concept;
? name the term that is opposite in meaning (antonym);
? what is the name of the value α, write down the formula on the board;
? which means α=0.8 and α=0.2
- the process of dissolving salt in water
? define this term
? What is wrong with Vanya?
Vanya and hydrolysis
Lying at home on the couch, Vanya thought about hydrolysis.
“How many in the world,” thought Vanya, “there are acids and bases!
Somewhere I read once: there are chlorides and sulfates ...
And there is probably a lot of hydrochloric acid and sulfuric acid:
After all, yesterday we went to school that hydrolysis occurs in water! ..
And why do people go on vacation to the sea on a mountain?
If you swim there for a long time, you can stay without panties:
Any fabric easily dissolves acid ... "
Vanin, listening to the story, the class laughed for an hour.
- anions "run" to it
? How is the anode charged?
? name the term that is opposite in meaning (antonym)
- phenolphthalein in sodium carbonate solution
? write the equation for the hydrolysis of sodium carbonate on the board and explain why you gave that answer;
- hydrochloric, phosphoric, nitrogen ...
? define the term "acid" in terms of TED
- phenolphthalein in sodium chloride solution
? write the equation for the hydrolysis of sodium chloride on the board and explain why you gave that answer;
- sodium chloride, barium sulfate, potassium phosphate, copper nitrate…
? define the term "salt" in terms of TED
- Swedish scientist who created TED
- hydroxides in a different way
? define the term "foundation" in terms of TED
We solved the crossword puzzle and got the topic of our lesson vertically - “Ion exchange reactions”. Consider where in life we encounter ions and ion exchange. Let's remember under what conditions do ion exchange reactions go to completion?
- if there is a precipitate
- if gas is formed
- if a slightly dissociated substance (water) is formed
For better memorization, I suggest you learn a memory rhyme:
If it stands out gas- this time;
And it will turn out water- it's two;
And the insoluble product is precipitated ...
"There is sediment- we say.
This is the third important point.
The chemist will never forget the rules of exchange:
As a result, there will certainly begas or water,
drops out sediment- then - order!
Today we need to see this in practice.
☺ But before starting the laboratory work, let's open the next page of our magazine - the historical one.
In the 19th century, chemistry was a very dangerous business. The history of science is replete with examples of accidents, often fatal, as a result of explosions, fires and poisoning in chemical laboratories and chemical industries.
Often chemists of the past, suffocating from toxic fumes, ran out of their laboratories with tears in their eyes to breathe in a breath of fresh air and recover, but, having caught their breath, they returned to their workplace again, conducting new and new experiments, testing their guesses and assumptions. . Theoretical ideas were still poorly developed, and when setting up an experiment, the chemist often did not know what consequences his research might lead to. Once, an acquaintance of the famous French chemist Charles Wurtz (1817-1884) found him nervously pacing in front of his laboratory. When asked what he was doing, Wurtz reluctantly replied: - I'm waiting for the results of my experience.
To avoid such accidents, let's repeat the safety precautions when working in the laboratory. To do this, carefully read the description of the experiments, study the set of reagents and select those from the "Rules of Survival" that we will need in this work.
☺ And now let's move on to the practical page and start doing practical work.
Getting into acid - is there worse luck?
But he will endure without sighs, without crying.
But in alkalis, phenolphthalein
Not life will begin, but solid raspberries!
Questions.
Experience #1:
- What substance precipitated? (Answer: copper hydroxide)
- Why is copper hydroxide blue?
- Write the molecular equation for the reaction on the board.
- Write the full ionic equation for the reaction on the board.
- Write the equation for the reaction in abbreviated ionic form on the board.
- What substance precipitated? (Answer: barium sulfate)
- Write the molecular equation for the reaction on the board.
- Write the full ionic equation for the reaction on the board.
- Write the equation for the reaction in abbreviated ionic form on the board.
Experience #2:
- What gas was released as a result of the experiment? (Answer: carbon dioxide)
- Is carbonic acid a strong or weak electrolyte?
- Write the equation for the dissociation of carbonic acid.
- Name other weak acids that you know.
- Write the molecular equation for the reaction on the board.
6. Write the reaction equation in full ionic form on the board.
7. Write the reaction equation on the board in abbreviated ionic form.
8. Determine the oxidation state of carbon in salt and oxide. Is this reaction a redox reaction?
9. Where in everyday life do we encounter ions, ion exchange reactions? (hard water, ion-exchange water purifiers, ion engines, air ionizers, etc.)
Experience #3:
- Why was an indicator added to the test tube?
- What is the color of phenolphthalein in an acidic environment?
- Write the molecular equation for the reaction on the board.
3. Write the reaction equation on the board in full ionic form.
4. Write the reaction equation on the board in abbreviated ionic form.
5. Why was the indicator not added in the second experiment?
6. Write the reaction equation in molecular form on the board.
7. Write the reaction equation in full ionic form on the board.
8. Write the reaction equation on the board in abbreviated ionic form.
9. What is the name of the reaction of the interaction of an acid with a base to form a salt and water?
Make a general conclusion to the laboratory work. Submit a work report.
☺ We did a good job, it's time to relax. Let's open the "fabulous" page of our magazine. I will read you some stories related to ion exchange reactions. Listen carefully and try to explain what processes they describe.
Fairy tale "Magic Elixir", author Volotskaya Anastasia.
In a certain kingdom, in a certain state, there lived a king and a queen. And they had a beautiful daughter Iron Hydroxide. One day, an evil witch wandered into their kingdom. Seeing the beautiful princess and envying her beauty and intelligence, she turned our Hydroxide into a tree, calling it Ferric Chloride, and with an evil smile said: “Only one who will have knowledge of ion exchange can disenchant your daughter!” Parents lost their feet, looking for magicians and sorcerers all over the country, but no one could help their grief. 17 years have passed. And in their small kingdom, a young scientist appeared who loved nature and was fond of alchemy. He got a job as a gardener in the royal park. One evening, walking in the park, the queen told the gardener about their grief. The young man was not in vain fond of chemistry and gladly agreed to help his inconsolable parents. Having prepared a magical elixir, he watered the roots of the tree and it turned into a princess again. So the gardener-chemist and his elixir saved the beauty from the witchcraft of the evil sorceress.
What substance did the magic elixir contain? Write an equation for the ion exchange reaction, as a result of which the enchanted tree turned into a princess.
Answer: alkali; FeCl3 + MeOH = Fe(OH) 3 ↓+MeCl 3
Story "Accident in Substance", author Budycheva Katrin.
In one large country, called Substances, there lived kind and hardworking little men. One sunny hot day, terrible news spread throughout the country. The main chemical plant for water purification failed. The most important reagent, aluminum hydroxide, has run out. The population was asked to find the substances needed to obtain it - aluminum chloride and sodium hydroxide. Everyone fussed, ran, and in less than an hour, the necessary reagents were found and brought to the plant.
Everyone was waiting impatiently for the reaction to begin. And finally, we got the long-awaited aluminum hydroxide. The foundation was flawless. The plant started working again, purifying the water, and has never broken down since.
Write a reaction equation for the process of obtaining aluminum hydroxide. (Answer: AlCl3 + 3NaOH = Al(OH) 3 ↓ + 3NaCl)
Why is it inconvenient to receive Al(OH)3 in this manner? (Answer: it dissolves in Al(OH) alkalis3 + NaOH = Na(Al(OH) 4 )) sodium aluminate hydrate)
Come up with a more convenient way to get Al(OH)3 . (Answer:
- From soda Na 2 SO 3 :
3Na 2 SO 3 + 2 AlCl 3 + 3H 2 O \u003d 2Al (OH) 3 ↓+ 6 NaCl + CO 2
- From salts with ammonia:
Al 2 (SO 4 ) 3 + 6NH 3 + 6H 2 O = 2Al(OH) 3 ↓ + 3 (NH 4 ) 2 SO 4
Fairy tale " About a beautiful princess and one hero”, author Reshetnikova Olga
In a certain kingdom, in a certain state, there lived the king Foundation with the queen Acid. And their daughter Salt grew up with them. Her father and mother doted on her. Here, once a foreign ship came to this city. The ship's captain was a merchant2 A. And he began to show outlandish goods, unprecedented miracles and reactions. The princess began to ask her parents: “Let me go to look at the wonders of overseas!” Her father and mother released her. Just climbed onto the deck of the ship beautiful salt, like insidious2 O, captivated by her beauty and grace, locked the princess in a richly decorated cabin, and gave the order to sail. They quickly raised all the sails and the ship ran through the waves. The king sent the base behind them in pursuit of his faithful guards - a detachment of ions - led by a young hero Sulfate of silver. They caught up with the overseas ship, freed the girl from the captivity and set off for their native lands. At home, table salt and silver sulfate were married, and there was a feast for the whole world. And their children were born, and our newlyweds lived happily ever after. After all, it’s not for nothing that they say that plus and minus stretch!
What were the names of the father and mother of Salt (Answer: NaOH and HCl)
What did they call their children Salt and Silver Sulfate (Answer: Silver Chloride)
Why did Salt not want to marry a merchant?
☺ The last page is the final one. Today in the lesson we have in practice consolidated information about ion exchange reactions, neutralization reactions. To summarize the lesson, we will conduct a chemical dictation.
Dictation.
Write down the words - antonyms (select terms that are opposite in meaning to the data),
- dissociation -
- anode -
- cation -
- oxidizer -
- acid properties -
- starting materials -
- metal -
- electron donor -
Grading a lesson.
Appendix
Memory rhymes
If it stands outgas- this time;
And it will turn outwater- it's two;
And the insoluble product is precipitated ...
"There issediment- we say.
This is the third important point.
The chemist will never forget the rules of exchange:
As a result, there will certainly begasorwater,
drops outsediment- then - order!
Getting into acid - is there worse luck?
But he will endure without sighs, without crying.
But in alkalis, phenolphthalein
Life will not begin, but continuousraspberries!
Practical work
Topic:Properties of acids, bases, salts.
Experience #1:Reactions proceeding with the formation of a precipitate.
Pour 3-4 ml of copper(2) sulfate solution into a test tube and add a little sodium hydroxide solution.
Pour 3-4 ml of aluminum sulfate into another test tube and add a solution of barium nitrate.
Write the equations of the ongoing reactions in molecular, ionic and abbreviated ionic form. Explain why precipitation formed. Solutions of what other substances can be poured into test tubes to precipitate?
Experience #2:Reactions that go with the release of gas.
Pour 3-4 ml of sodium carbonate into a test tube and add a little hydrochloric acid solution.
Write an equation for the ongoing reaction in molecular, ionic, and abbreviated ionic form.
Experience #3:Reactions proceeding with the formation of a low-dissociating substance.
Pour 3-4 ml of sodium hydroxide into one test tube and add 2-3 drops of phenolphthalein. The solution takes on a crimson color. Then pour hydrochloric acid solution until discoloration.
In another test tube, pour about 10 ml of copper(2) sulfate and add some sodium hydroxide. A blue precipitate of copper(2) hydroxide is formed. Pour sulfuric acid into the test tube until the precipitate dissolves.
Write the equations of the ongoing reactions in molecular, ionic and abbreviated ionic form. Explain why discoloration occurred in the first test tube, and dissolution of the precipitate in the second.
Answers to the crossword
1 d | And | from | from | about | c | And | but | c | And | I | |||||||||||||||||
2 G | And | d | R | about | l | And | h | ||||||||||||||||||||
3 but | n | about | d | ||||||||||||||||||||||||
4 m | but | l | And | n | about | in | s | th | |||||||||||||||||||
5 to | And | from | l | about | T | s | |||||||||||||||||||||
6 b | e | from | c | in | e | T | n | s | th | ||||||||||||||||||
7 from | about | l | And | ||||||||||||||||||||||||
8 but | R | R | e | n | And | at | from | ||||||||||||||||||||
9 about | from | n | about | in | but | n | And | I |
Tasks.
1. Although plants and animals need phosphorus compounds as an element that is part of vital substances, pollution of natural waters with phosphates has an extremely negative effect on the state of water bodies. The discharge of phosphates with sewage causes the rapid development of blue-green algae, and the vital activity of all other organisms is inhibited. Determine the number of cations and anions formed during the dissociation of 25 mol of sodium orthophosphate.
Solution:
Na3 PO4 ↔ 3Na+ +PO4 3-
= 25 3 = 75 mol
= 25 1 = 25 mol
Answer: 25 mol PO4 3-- ; 75 mol Na+
electrolytic dissociation. Acids and bases in aqueous solution. Hydrolysis. Tasks for independent solution
6.1. Although plants and animals need phosphorus compounds as an element that is part of vital substances, pollution of natural waters with phosphates has an extremely negative effect on the state of water bodies. The discharge of phosphates with sewage causes the rapid development of blue-green algae, and the vital activity of all other organisms is inhibited. Determine the number of cations and anions formed during the dissociation of 25 mol of sodium orthophosphate.
6.2. The acidity of the soil, as well as the acidity of aqueous solutions, is estimated by pH, which is measured by making an aqueous "extract" (shake a soil sample weighing 10 g with 10 ml of water and allow solid particles to settle). When the soil contains almost no acids (neutral), it is good for carrots, cabbage, onions, garlic, celery, asparagus, radishes, turnips, sunflowers, as well as currants, plums, cherries and apple trees. With a pH value of 4 to 5, the soil is slightly acidic. On such soil, peas, beans, cucumbers, radishes, tomatoes, lettuce, cauliflower and spinach give a good harvest. What is the molar concentration of H+ in the water extract of such soil?
6.3. Acid rain (a consequence of human activity: when various fuels (gasoline, kerosene, oil, coal) are burned, a huge amount of sulfur dioxide and nitrogen dioxide is released into the atmosphere. Interacting with atmospheric oxygen and atmospheric moisture, these oxides turn into sulfuric and nitric acids. Determine the value The pH of natural waters, which are obtained from gas emissions from a chemical plant, containing 10 kg of nitrogen dioxide and 20 kg of sulfur dioxide.The volume of water in which the resulting nitric and sulfuric acids will be dissolved, take equal to 10,000 m3 .
6.4. To reduce the acidity, the soil is subjected to liming. The benefits of liming acidic soils have been known for three thousand years BC. Ancient Egyptian farmers noticed that red and yellow soils, located near limestone quarries, were more productive. As a result of liming the soil, a chemical reaction occurs in it: 2H+ + CaCO3 = Ca2+ + CO2 + H2 O. Calculate the amount of CO2 (at n.o.), which is released when 200 l of water with a pH value of 3.3 is treated with an excess of CaCO3 .
6.5. Pure water (pH = 7), being in the air, dissolves the carbon dioxide present in the atmosphere, so its pH becomes 6.5-6.8 over time. Determine a) the molar concentration of cations H+ in water if pH = 6.7; b) the molar concentration of carbonic acid H2 CO3 formed in this case (the degree of dissociation is 1%).
6.6. During an accident at a warehouse of toxic substances, 0.05 kg of dangerous phosgene gas, carbon monoxide CCl, leaked2 O. The decontamination team arrived and sprayed the warehouse area with water from a fire hose. When sprayed with water, phosgene undergoes irreversible hydrolysis to form carbon dioxide and hydrogen chloride. Determine the pH of the resulting water effluents, if a total of 10 m3 was consumed during degassing3 water.
6.7. In 1974, Scotland recorded a European "record" for the acidity of precipitation. The pH value for rainwater was found to be 2.4. Calculate for this case the concentration of cations H+ in Scottish acid rain.
6.8. Due to the strong pollution of the atmosphere with sulfur oxides in the area of the Anshan Iron and Steel Works in China, precipitation with a pH value of 2.25 fell in 1981. Calculate the mass fraction of sulfuric acid contained in this "acid rain".
Answers
6.1. 25 mol PO4 3-- ; 75 mol Na+
6.2. H concentration+ from 1 . 10 --5 up to 1 . 10 --4 mol/l
6.3. pH = 4.1
6.4. 1.12 l
6.5. [N+ ] = 2 . 10 --7 mol/l;c(H2 CO3 ) = 1 . 10 --5 mol/l
6.6. pH = 4
6.7. [N+ ] = 4 . 10 --3 mol/l
6.8. [N+ ] = 5,6 . 10 --3 mol/l
