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Recovery reactions. Classification of OVR. Lesson objectives: 1. educational - to systematize students’ knowledge about the classification of chemical reactions in the light of electronic theory; - teach to explain the basic concepts of OVR; - give a classification of ODD 2. developing - develop the ability to observe, draw conclusions; - continue the development of logical thinking, analysis and comparison skills; 3. educational - to form the scientific worldview of students, improve work skills; -develop the ability to listen to each other, analyze the situation, improve the culture of interpersonal communication
Basic concepts: redox reactions, oxidizer, reducer, oxidation processes, reduction reactions, intermolecular intramolecular disproportionations Equipment: PSHE D. I. Mendeleeva
When certain types of chemical bonds are formed, the process of adding electrons to an atom or giving them away occurs, so the formation of common electron pairs or charged particles - cations and anions - is possible. The reduction process is the process of accepting electrons by an atom (particle) +n. As a result, a decrease in the oxidation state is observed. during restoration - s.o. decreases For example +2 Task. Write the process of copper reduction () The oxidation process is the process of giving up electrons by an atom (particle) n As a result, an increase in the degree of oxidation is observed. during oxidation - s.o. increases For example Task. Write the oxidation process of aluminum ()
Oxidizing agent and reducing agent. The ability to determine the functions of a substance/particle (oxidizing or reducing) by s.o. element Reducing agent - particle, atom, molecule that donates electrons (electron donor). The reducing agent always increases the d.o. An oxidizing agent is a particle, atom, molecule that accepts electrons (electron recipient). The oxidizing agent always lowers the s.o. 1. So, if in a compound the element is in the minimum r.o., like sulfur in (-2 is the minimum r.o. of sulfur / group number -8 /), then the compound acts as a reducing agent. For example: ... 2. If in the compound the element is at maximum s. o., like sulfur in - the compound acts as an oxidizing agent. For example: H ...
The most important Oxidizing and Reducing Agents Oxidizing agents: K H And also some simple substances Reducing agents H H And also some simple substances Metals, CO, C Task: Find oxidizing and reducing agents HN S CuO among the proposed compounds
All chemical reactions that occur with a change in d.o. elements are called redox.
Intermolecular ORR - exchange of electrons occurs between different atoms (molecules, ions) - the oxidizing agent and the reducing agent are in different molecules: + = Reactions of intramolecular oxidation and reduction - the oxidizing agent and the reducing agent are in the same substance (molecule, particle) = + 2 Reactions disproportionation (dismutation) - reactions in which the same element acts both as an oxidizing agent and as a reducing agent, and as a result of the reaction, compounds are formed that contain the same chemical element in different d.o. K _________________________________________________________________ Assignment What type of OVR is the reaction: N + + HN
PIN 2 𝑆+𝑆 = 3S + 2 O Is the reaction ORR? Determine the oxidation state of elements Find an oxidizing agent, a reducing agent Determine the type of ORR HOMEWORK 1. p. 11, learn 2. write out ORR of all types from the text (two examples each)
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Completed by: Chemistry teacher Baimukhametova Batila Turginbaevna Oxidation-reduction reactions
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The motto of the lesson is “Someone loses, but someone finds...” By working, you will do everything for your loved ones and for yourself, and if there is no success during your work, failure is not a problem, try again. D. I. Mendeleev.
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Lesson topic: “Redox reactions” Purpose: To get acquainted with redox reactions and find out what is the difference between metabolic reactions and redox reactions. Learn to identify oxidizing and reducing agents in reactions. Learn to draw diagrams of the processes of giving and receiving electrons. Learn about the most important redox reactions found in nature.
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Perhaps these electrons are Worlds where there are five continents, Arts, knowledge, wars, thrones And the memory of forty centuries! Also, perhaps, every atom is a Universe with a hundred planets; There is everything that is here, in a compressed volume, But also what is not here. V. Brusosova.
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What is oxidation state? The oxidation state is the nominal charge of an atom of a chemical element in a compound, calculated based on the assumption that all compounds consist only of ions. The oxidation state can be positive, negative or zero, depending on the nature of the compounds involved. Some elements have constant oxidation states, others have variable ones. Elements with a constant positive oxidation state include - alkali metals: Li+1, Na+1, K+1, Rb+1, Cs+1, Fr+1, the following elements of group II of the periodic table: Be+2, Mg+2, Ca+2, Sr+2, Ba+2, Ra+2, Zn+2, as well as element III A of group - A1+3 and some others. Metals in compounds always have a positive oxidation state. Of non-metals, F has a constant negative oxidation state (-1). In simple substances formed by atoms of metals or non-metals, the oxidation states of elements are zero, for example: Na°, Al°, Fe°, H2, O2, F2, Cl2, Br2. Hydrogen is characterized by oxidation states: +1 (H20), -1 (NaH). Oxygen is characterized by oxidation states: -2 (H20), -1 (H2O2), +2 (OF2).
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The most important reducing agents and oxidizing agents Reducing agents: Oxidizing agents: Elementary metals Hydrogen Carbon Carbon monoxide (II) (CO) Hydrogen sulfide (H2S) Sulfur oxide (IV) (SO2) Sulfurous acid H2SO3 and its salts Hydrohalic acids and their salts Metal cations in intermediate states oxidation: SnCl2, FeCl2, MnSO4, Cr2(SO4)3 Nitrous acid HNO2 Ammonia NH3 Nitrogen oxide (II) (NO) Halogens Potassium permanganate (KMnO4) Potassium manganate (K2MnO4) Manganese oxide (IV) (MnO2) Potassium dichromate (K2Cr2O7) Nitric acid (HNO3) Sulfuric acid (conc.H2SO4) Copper(II) oxide (CuO) Lead(IV) oxide (PbO2) Hydrogen peroxide (H2O2) Iron(III) chloride (FeCl3) Organic nitro compounds
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The degree of oxidation of manganese in the potassium permanganate compound KMnO4. 1. Oxidation state of potassium +1, oxygen -2. 2. Let's count the number of negative charges: 4 (-2) = - 8 3. The number of positive charges on manganese is 1. 4. Let's make the following equation: (+1) + x+ (-2)*4 =0 1+ x - 8=0 X = 8 - 1 = 7 X= +7 +7 is the oxidation state of manganese in potassium permanganate.
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Rules for determining oxidation states 1. The oxidation state of an element in a simple substance is 0. For example: Ca, H2, Cl2, Na. 2. The oxidation state of fluorine in all compounds except F2 is – 1. Example: S+6F6-1 3. The oxidation state of oxygen in all compounds except O2, O3, F2-1O+2 and peroxide compounds Na2+1 O- 12; H2+1O-12 is equal to –2 Examples: Na2O-2, BaO-2, CO2-2. 4. The oxidation state of hydrogen is +1 if the compounds contain at least one non-metal, -1 in compounds with metals (hydrides) 5. The oxidation state of O in H2 Examples: C-4H4+1 Ba+2H2-1 H2 The oxidation state of metals always positive (except for simple substances). The oxidation state of metals of the main subgroups is always equal to the group number. The degree of oxidation of side subgroups can take different values. Examples: Na+ Cl-, Al2+3O3-2, Cr2+3 O3-2, Cr+2O-2. 6. The maximum positive oxidation state is equal to the group number (exceptions: Cu+2, Au+3). The minimum oxidation state is equal to the group number minus eight. Examples: H+1N+5O-23, N-3H+13. 7. The sum of the oxidation states of atoms in a molecule (ion) is equal to 0 (the charge of the ion).
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Laboratory work Safety rules. Experiment 1. Carry out a chemical reaction between solutions of copper (II) sulfate and sodium hydroxide. Experiment 2. 1. Place an iron nail in a solution of copper (II) sulfate. 2. Make up equations for chemical reactions. 3. Determine the type of each chemical reaction. 4. Determine the oxidation state of the atom of each chemical element before and after the reaction. 5. Think about how these reactions differ?
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Answers: Cu+2S+6O4-2 +2Na +1O-2H+1Cu +2(O -2H+1)2+Na2 +1S +6O4-2 – exchange reaction Cu+2S+6O4-2 + Fe0 Fe+2 S+6O4 -2+Сu0 – substitution reaction Reaction No. 2 differs from reaction No. 1 in that in this case the oxidation state of the atoms of chemical elements changes before and after the reaction. Note this important difference between the two reactions. The second reaction is OVR. Let us underline in the reaction equation the symbols of the chemical elements that changed the oxidation state. Let's write them down and indicate what the atoms did with their electrons (Give or receive?), i.e. electron transitions. Cu+2 + 2 e- Cu0 – oxidizing agent, reduced Fe0 - 2 e- Fe+2 – reducing agent, oxidized
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Classification of redox reactions 1. Intermolecular redox reactions The oxidizing agent and the reducing agent are found in different substances; the exchange of electrons in these reactions occurs between different atoms or molecules: 2Ca0 + O20 → 2 Ca+2O-2 Ca - reducing agent; O2 - oxidizing agent Cu+2O + C+2O → Cu0 + C+4O2 CO - reducing agent; CuO – oxidizing agent Zn0 + 2HCl → Zn+2Cl2 + H20 Zn – reducing agent; HСl - oxidizing agent Mn+4O2 + 2KI-1 + 2H2SO4 → I20 + K2SO4 + Mn+2SO4 + 2H2O KI - reducing agent; MnO2 is an oxidizing agent.
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2. Intramolecular redox reactions In intramolecular reactions, the oxidizing agent and the reducing agent are in the same molecule. Intramolecular reactions usually occur during the thermal decomposition of substances containing an oxidizing agent and a reducing agent. 4Na2Cr2O7 → 4Na2CrO4 + 2Cr2O3 + 3O2 Cr+6- oxidizing agent; O-2 - reducing agent
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3. Disproportionation reactions Redox reactions in which one element simultaneously increases and decreases the oxidation state. 3S + 6NaOH → Na2SO3 + 2Na2S + 3H2O Sulfur in oxidation state 0 is both an oxidizing agent and a reducing agent. 4. Comporportionation reactions Redox reactions in which atoms of one element in different oxidation states acquire one oxidation state as a result of the reaction. 5NaBr + NaBrO3 + 3H2SO4 → 3Na2SO4 + 3Br2 + 3H2O Br+5 – oxidizing agent; Br-1 – reducing agent
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Algorithm for composing equations of redox reactions using the electronic balance method 1. Write down the reaction scheme KMnO4+KI+H2SO4→MnSO4+ I2+K2SO4+H2O 2. Enter the oxidation states of the atoms of the elements for which it changes KMn+7O4+ KI-+ H2SO4→ Mn+2SO4+ I20+ K2SO4+ H2O 3. Elements that change oxidation states are identified and the number of electrons accepted by the oxidizing agent and donated by the reducing agent is determined. Mn+7 + 5ē → Mn+2 2I-1 - 2ē → I20 4. Equalize the number of accepted and donated electrons, thereby establishing coefficients for compounds that contain elements that change the oxidation state. Mn+7 + 5ē → Mn+22 2I-1 - 2ē → I205 2Mn+7 + 10I-1 → 2Mn+2 + 5I20 5. Select coefficients for all other participants in the reaction. 2KMnO4+10KI+8H2SO4→2MnSO4+5I2+6K2SO4+ 8H2O
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Electronic balance is a method of finding coefficients in the equations of redox reactions, which considers the exchange of electrons between atoms of elements that change their oxidation state. The number of electrons donated by the reducing agent is equal to the number of electrons accepted by the oxidizing agent.
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Oxidation-reduction reactions are reactions in which oxidation and reduction processes occur simultaneously and, as a rule, the oxidation states of elements change. Let's consider the process using the example of the interaction of zinc with dilute sulfuric acid:
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Let's remember: 1. Oxidation-reduction reactions are reactions in which electrons transfer from one atom, molecule or ion to another. 2. Oxidation is the process of losing electrons, and the degree of oxidation increases. 3. Reduction is the process of adding electrons, the oxidation state decreases. 4.Atoms, molecules or ions that donate electrons are oxidized; are reducing agents. 5.Atoms, ions or molecules that accept electrons are reduced; are oxidizing agents. 6. Oxidation is always accompanied by reduction; reduction is associated with oxidation. 7. Oxidation-reduction reactions are the unity of two opposite processes: oxidation and reduction.
The topic of the project is "Oxidation-reduction reactions."
Creative project name "Someone loses, and someone finds...".
Project coordinator Drobot Svetlana Sergeevna, chemistry teacher, [email protected]
Academic subject - chemistry.
Eleventh grade students took part in the project.
The project was carried out from October to December (3 months) in the 11th grade.
Subject "Redox reactions" runs like a red thread through the entire chemistry course at school (8th, 9th and 11th grades) and is very difficult to understand the processes occurring as a result of these reactions.
Fundamental question: Is the end of the world possible?
The following were formulated on this topic: problematic issues:
1.Where in the world around us do we meet with ODD?
2.What is the difference between metabolic reactions and redox reactions?
3.What is the difference between oxidation state and valency?
4.What are the features of ORR in organic chemistry?
Problematic questions were compiled in such a way as to show in as much detail as possible all the phenomena associated with redox processes occurring in the world around us and to arouse children’s interest in studying these complex chemical processes.
The students carried out research work on the problematic issues posed to them. They worked in two directions. Some conducted research considering ORR as a chemical process:
1. Valency and oxidation state.
4. OVR in organic chemistry.
3. What is OVR and what is RIO.
4. Anode + cathode = electrolysis
5. Redox reactions
And others from the point of view of the practical significance of these processes:
1. In the kingdom of the red devil.
2. Are you not wearing white yet? Then we are coming to you!
3. Seven wonders in living and inanimate nature.
4. This Victory Day...
The presentation “In the Kingdom of the Red Devil” can be used not only as a research paper, but also in chemistry lessons when explaining this topic because it explains the concept of corrosion, the essence of this process, classification - chemical, electrochemical, mechanochemical; methods of protection against corrosion. And the material: types of corrosion, Do you know what... is beyond the scope of the curriculum.
The presentation “Are you wearing white yet?...” talks about the use of redox reactions in everyday life. Washing in a scientific way - removing iodine stains, stains of various types; recommendations for handling products made from natural wool; about the composition of powders and the role of one or another component in washing.
"Seven wonders of living and inanimate nature." This presentation talks about the seven wonders of living and inanimate nature - combustion, metal corrosion, explosion, electrolysis, rotting, fermentation, photosynthesis. As a result, the conclusion was drawn: these seven wonders of living and inanimate nature relate to the redox reactions that surround us and play a huge role in our lives.
"This Victory Day." Application of redox reactions in war.
The creative result of students' research work becomes an educational website. The site combines all the material on the topic. It also contains a verification test that allows you to test your knowledge and get a grade. The advantage of this site is that it is accessible to any student via the Internet.
Summing up the results of their research work, the students came to the conclusion that the entire world around us can be considered as a giant chemical laboratory, in which chemical reactions, mainly redox ones, take place every second, and as long as redox processes exist in nature, the end of the world is impossible.
During the work on the project, didactic material was developed (tests, methods for determining valency, oxidation state; compiling ORR using the electronic balance method, compiling ORR using the half-reaction method, rules for compiling ion exchange reactions).
While working on the project, a large amount of scientific, methodological, and popular science literature was used.
Internet resources were also used.
Our project will help students independently understand the difficult issues of this topic, as well as prepare for the Unified State Exam in chemistry.
The entire world around us can be considered as a giant chemical laboratory, in which chemical reactions, mainly redox ones, take place every second.
Oxidation is the process of losing electrons by an atom, molecule or ion. The atom turns into a positively charged ion: Zn 0 – 2e Zn 2+ the negatively charged ion becomes a neutral atom: 2Cl - -2e Cl 2 0 S 2- -2e S 0 The size of the positively charged ion (atom) increases according to the number of electrons given up: Fe 2 + -1e Fe 3+ Mn +2 -2e Mn +4
Reduction is the process of gaining electrons by an atom, molecule or ion. The atom turns into a negatively charged ion S 0 + 2e S 2 Br 0 + e Br The size of a positively charged ion (atom) decreases according to the number of attached electrons: Mn e Mn +2 S e S +4 or it can transform into a neutral atom: H + + e H 0 Cu e Cu 0
Reducing agents are atoms, molecules or ions that donate electrons. They are oxidized during the redox process. Typical reducing agents: metal atoms with large atomic radii (I-A, II-A groups), as well as Fe, Al, Zn, simple non-metal substances: hydrogen, carbon, boron; negatively charged ions: Cl, Br, I, S 2, N 3. Fluoride ions F are not reducing agents. Metal ions in the lowest concentration: Fe 2+, Cu +, Mn 2+, Cr 3+; complex ions and molecules containing atoms with intermediate residues: SO 3 2, NO 2; CO, MnO 2, etc.
Oxidizing agents are atoms, molecules or ions that gain electrons. They are reduced during the redox process. Typical oxidizing agents: atoms of non-metal groups VII-A, VI-A, V-A in the composition of simple substances, metal ions in the highest concentration: Cu 2+, Fe 3+, Ag + ... complex ions and molecules containing atoms with higher and higher d.s.: SO 4 2, NO 3, MnO 4, СlО 3, Cr 2 O 7 2-, SO 3, MnO 2, etc.
Sulfur oxidation states: -2.0,+4,+6 H 2 S -2 - reducing agent 2H 2 S+3O 2 =2H 2 O+2SO 2 S 0.S +4 O 2 - oxidizing agent and reducing agent S+O 2 =SO 2 2SO 2 +O 2 =2SO 3 (reducing agent) S+2Na=Na 2 S SO 2 +2H 2 S=3S+2H 2 O (oxidizing agent) H 2 S +6 O 4 - oxidizing agent Cu+2H 2 SO 4 =CuSO 4 +SO 2 +2H 2 O
Determination of oxidation states of atoms of chemical elements С.о. chemical atoms in the composition of a simple substance = 0 Algebraic sum of s.o. of all elements in the ion is equal to the charge of the ion Algebraic sum s.o. of all elements in the composition of a complex substance is 0. K +1 Mn +7 O x+4(-2)=0
Classification of redox reactions Intermolecular oxidation reactions 2Al 0 + 3Cl 2 0 2Al +3 Cl 3 -1 Intramolecular oxidation reactions 2KCl +5 O KCl O 2 0 Reactions of disproportionation, dismutation (auto-oxidation-self-reduction): 3Cl KOH (hor.) KCl + 5 O 3 +5KCl -1 +3H 2 O 2N +4 O 2 + H 2 O HN +3 O 2 + HN +5 O 3
This is useful to know. The oxidation states of the elements in the composition of the salt anion are the same as in the acid, for example: (NH 4) 2 Cr 2 +6 O 7 and H 2 Cr 2 +6 O 7 The oxidation state of oxygen in peroxides is -1 Oxidation state sulfur in some sulfides is -1, for example: FeS 2 Fluorine is the only non-metal that does not have a positive oxidation state in compounds. In compounds NH 3, CH 4 and others, the sign of the electropositive element hydrogen is in second place
Oxidative properties of concentrated sulfuric acid Products of sulfur reduction: H 2 SO 4 + very active. metal (Mg, Li, Na...) H 2 S H 2 SO 4 + act. metal (Mn, Fe, Zn...) S H 2 SO 4 + inactive. metal (Cu, Ag, Sb...) SO 2 H 2 SO 4 + HBr SO 2 H 2 SO 4 + non-metals (C, P, S...) SO 2 Note: it is often possible to form a mixture of these products in different proportions
Hydrogen peroxide in redox reactions Solution medium Oxidation (H 2 O 2 -reducing agent) Reduction (H 2 O 2 -oxidizing agent) acidic H 2 O 2 -2eO 2 + 2H + (O – 2eO 2 0) H 2 O 2 + 2H + +2e2H 2 O (O e2O - 2) alkaline H 2 O 2 +2OH -O 2 +2H 2 O (O – 2eO 2 0) H 2 O 2 +2e2OH - (O e2O - 2) neutral H 2 O 2 - 2eO 2 + 2H + (O – 2eO 2 0) H 2 O 2 + 2e2OH - (O e2O - 2)
Nitric acid in redox reactions Nitrogen reduction products: Concentrated HNO 3: N +5 +1e N +4 (NO 2) (Ni, Cu, Ag, Hg; C, S, P, As, Se); passivates Fe, Al, Cr Dilute HNO 3: N +5 +3e N +2 (NO) (Metals in EHRNM Al...Cu; non-metals S, P, As, Se) Dilute HNO 3: N +5 +4e N +1 (N 2 O) Ca, Mg, Zn Dilute HNO 3: N +5 +5e N 0 (N 2) Very dilute: N e N -3 (NH 4 NO 3) (active metals in EHRNM to Al)
The Meaning of OVR OVR is extremely common. They are associated with metabolic processes in living organisms, respiration, decay, fermentation, photosynthesis. OVRs ensure the circulation of substances in nature. They can be observed during fuel combustion, corrosion and metal smelting. With their help, alkalis, acids and other valuable chemicals are obtained. OVRs underlie the conversion of the energy of interacting chemicals into electrical energy in galvanic batteries.
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