Chemistry presentation "Chemical equilibrium. Factors affecting chemical equilibrium"

To use the preview of presentations, create a Google account (account) and sign in: https://accounts.google.com

Slides captions:

CHEMICAL EQUILIBRIUM and ways to shift it

Chemical equilibrium The state of equilibrium is characteristic of reversible chemical reactions. A reversible reaction is a chemical reaction that, under the same conditions, can go in the forward and reverse directions. Irreversible is a reaction that goes almost to the end in one direction.

In all reversible reactions, the rate of the forward reaction decreases and the rate of the reverse reaction increases until both rates become equal and an equilibrium state is established.

Chemical equilibrium is the state of a system in which the rate of the forward reaction is equal to the rate of the reverse reaction.

The concentrations of all substances in a state of equilibrium (equilibrium concentrations) are constant. Chemical equilibrium has a dynamic character. This means that both the forward and reverse reactions do not stop at equilibrium.

The shift of equilibrium in the desired direction is achieved by changing the reaction conditions (Le Chatelier's principle). Le Chatelier's principle - If an external influence is exerted on a system in a state of equilibrium, then the system will move to another state in such a way as to reduce the effect of external influence.

For a one-stage reversible reaction at equilibrium, the expressions for the rates of direct V 1 and reverse reactions V 2 have the form: where [a], [b], [c] and [d] are the equilibrium molar concentrations of substances a, b, c and d; a,b,c and d are the corresponding stoichiometric coefficients (assuming that the reaction proceeds in one stage); k1 and k2 are coefficients of proportionality, called rate constants.

From the equilibrium condition V 1 = V 2 it follows: From here we obtain the expression for the equilibrium constant K p: The higher the value of K p, the more direct reaction products in the equilibrium mixture.

The influence of temperature on the shift in equilibrium Reactions accompanied by the release of heat are called exothermic. Reactions that absorb heat are called endothermic. For each reversible reaction, one of the directions corresponds to an exothermic process, and the other to an endothermic one.

The influence of temperature on the shift of equilibrium To shift the equilibrium to the right (for an exothermic reaction) --- you need to lower the temperature. And for endothermic --- on the contrary, increase the temperature.

As the temperature rises, the chemical equilibrium shifts in the direction of the endothermic reaction, and as the temperature decreases, in the direction of the exothermic reaction.

Influence of concentration on the equilibrium shift Equilibrium will shift to the RIGHT if: Increase the concentration of one of the reactants Remove the product from the reaction zone

Influence of pressure on the shift of equilibrium The influence of pressure on the state of equilibrium is manifested only in the presence of gases in the system!!!

Influence of pressure on the shift of equilibrium With increasing pressure, the equilibrium shifts in the direction of the formation of substances (initial or products) with a smaller volume; when the pressure decreases, the equilibrium shifts in the direction of the formation of substances with a large volume

N 2 + 3 H 2 2 NH 3 + Q With increasing pressure, the equilibrium will shift to where there are fewer moles (where there are fewer volumes) !!! 1 mol 3 mol 2 mol

Catalysts do not affect the equilibrium position!

In which direction will the balance shift?

The concentration of which substances should be increased in order to shift the equilibrium 2NO + Cl 2 = 2NOCl + Q to the left? a) NO; b) Cl 2 ; c) NOCl; d) will change over time.

On the topic: methodological developments, presentations and notes

PRESENTATION ON MUSIC GRADE 5 "ILLUSTRATIONS FOR LESSONS IN GRADE 5"

This presentation contains material for music lessons in the 5th grade according to the program of D.B. Kabalevsky. Topic: "Music and fine arts" .......

Physics presentation Grade 10 Temperature and thermal equilibrium. Temperature determination. Absolute temperature is a measure of the average kinetic energy of molecules.

Presentation in physics Grade 10 on the topic "Temperature and thermal equilibrium. Determination of temperature. Absolute temperature is a measure of the average kinetic energy of molecules." Textbook G, I, Myakishev, B.B ....

Presentation for the lesson of studying a new topic + physical dictation for repetition on the topic "Mechanical work. Power" ...

reversible reactions. chemical balance. Test - generalization on topics The test is compiled based on the materials of the collections of preparation for the exam (d). Chemistry teacher MBOU MO Nyagan "Secondary School 6" Kim N.V.

A1. A reversible chemical reaction is: 1) hydrolysis of iron(III) chloride; 2) combustion of natural gas; 3) boiling eggs; 4) cement hardening. A2. The following salt undergoes reversible hydrolysis: 1) iron sulfide; 2) calcium carbide; 3) sodium sulfite; 4) sodium chloride.

A3. The initial rate of dissolution of zinc in hydrochloric acid does not depend on: 1) the degree of grinding of zinc; 2) temperature of HCl solution; 3) HCl concentration; 4) the size of the test tube. A4. The state of chemical equilibrium is characterized by: 1) the cessation of the flow of direct and reverse chemical reactions; 2) the equality of the rates of direct and reverse reactions; 3) equality of the total mass of products to the total mass of reagents; 4) the equality of the total amount of the substance of the products to the total amount of the substance of the reagents.

2NO (g) + O 2 (g) 2NO 2 (g) + Q A5. The reversible reaction 2NO (g) + O 2 (g) 2NO 2 (g) + Q is in equilibrium. Under what conditions will the rate of the reverse reaction increase more than the rate of the forward reaction? 1) Pressure reduction; 2) temperature increase; 3) increase in pressure; 4) the use of a catalyst. CH 3 OH + HCOOH HCOOCH 3 + H 2 O - Q A6. To increase the yield of an ester in the chemical process CH 3 OH + HCOOH HCOOCH 3 + H 2 O - Q, you must: 1) add water; 2) reduce the concentration of formic acid; 3) increase the concentration of ether; 4) increase the temperature.

A7. According to the figure below for the reaction A + B C, determine the correct statement. The equilibrium in the reaction A + B C shifts as the temperature drops: 1) to the right, because it is an endothermic reaction; 2) to the left, because it is an exothermic reaction; 3) to the right, because it is an exothermic reaction; 4) to the left, because this is an endothermic reaction.

A8. When pressure changes, the chemical equilibrium does not shift in the following reaction: 1) CO (g) + Cl 2 (g) COCl 2 (g); 2) CO 2 (g) + C 2CO (g); 3) 2CO (g) + O 2 (g) 2CO 2 (g); 4) C + O 2 (g.) CO 2 (g.). A9. With an increase in pressure, the chemical equilibrium shifts towards: 1) an endothermic reaction; 2) exothermic reaction; 3) reducing the volume of the reaction mixture; 4) increasing the volume of the reaction mixture.

A10. The introduction of a catalyst into a system that is in a state of dynamic equilibrium: 1) will increase the rate of only the direct reaction; 2) increase the rate of only the reverse reaction; 3) increase the rate of both forward and reverse reactions; 4) does not affect the rate of either forward or reverse reactions.

PART B Reaction equation Conditions for the course of a chemical reaction a) N 2 + O 2 2NO; b) 2NO + O 2 2NO 2; c) C 6 H 6 + 3Cl 2 C 6 H 6 Cl 6; d) 2SO 2 + O 2 2SO 3. 1) Impossible under any circumstances; 2) during gas discharge; 3) when irradiated with intense UV light; 4) in the presence of a catalyst; 5) at room temperature. IN 1. Establish a correspondence between the reaction equations and the conditions under which they are possible.

Reaction Equation Chemical Reaction Conditions a) 2Na + Cl 2 = 2NaCl; b) 6CO 2 + 6H 2 O \u003d C 6 H 12 O 6 + 6O 2; c) CO + Cl 2 = COCl 2; d) HCOOH \u003d H 2 O + CO. 1) Irreversible chemical reaction proceeds with direct contact; 2) an irreversible chemical reaction that proceeds when heated in the presence of sulfuric acid; 3) reaction is impossible; 4) a reversible chemical reaction that proceeds when heated in the presence of a catalyst; 5) a reaction that is irreversible under photosynthesis conditions, proceeds in plant cells. IN 2. Establish a correspondence between the reaction equations and the conditions under which they are possible.

IN 3. Establish a correspondence between chemical concepts and their definitions. Chemical concept Definition Definition of the concept a) The rate of a chemical reaction; b) the mechanism of a chemical reaction; c) catalysis; d) chemical equilibrium. 1) The minimum energy that the reactants must receive in a chemical reaction in order to overcome the barrier that prevents the formation of products; 2) a value that numerically characterizes the intensity of the course of a chemical process, equal to the ratio of the change in the concentration of a substance to the change in time; 3) the sequence of elementary stages of a chemical reaction on the way of the transformation of reagents into products; 4) the state of a reversible reaction, when the rate of the forward reaction is equal to the rate of the reverse reaction; 5) the phenomenon of acceleration of a chemical reaction by certain substances that are not consumed as a result of a chemical process.

Energy effect process) Charging the battery; b) evaporation of water; c) ice crystallization; d) reaction of zinc with hydrochloric acid. 1) With the release of energy; 2) with energy absorption. AT 4. Establish a correspondence between processes and their thermal effects. Process Energy effect a) CCl 4 (l.) CCl 4 (g.); b) 2CH 2 O (g.) + 2O 2 (g.) 2CO 2 (g.) + 2H 2 O (l.); c) H 2 SO 4 (l.) H 2 SO 4 (water); d) N 2 (g) + O 2 (g) 2NO (g). 1) Endothermic; 2) exothermic. AT 5. Establish a correspondence between processes and their energy effects.

AT 6. Reactions occurring without a catalyst are: 1) 2C + O 2 = 2CO; 2) CO + 2H 2 = CH 3 OH; 3) 2KNO 3 \u003d 2KNO 2 + O 2; 4) C 6 H 6 + Cl 2 = C 6 H 5 Cl + HCl; 5) P 4 + 5O 2 \u003d 2P 2 O 5; 6) 4NH 3 + 5O 2 = 4NO + 6H 2 O. B7. Irreversible reactions are: 1) PCl 3 + Cl 2 = PCl 5; 2) Fe + CuSO 4 = FeSO 4 + Cu; 3) CO + H 2 = CH 2 O; 4) C + O 2 \u003d CO 2; 5) 2H 2 O 2 \u003d 2H 2 O + O 2; 6) Na 2 CO 3 + H 2 O = NaHCO 3 + NaOH.

AT 8. Chlorine irreversibly reacts with the following substances: 1) water; 2) calcium hydroxide; 3) hydrogen; 4) potassium iodide; 5) carbon monoxide; 6) methane when irradiated with light. AT 9. Substances, the dissolution of which in water is accompanied by the absorption of energy, are: 1) calcium oxide; 2) sulfuric acid; 3) sodium chloride; 4) potassium nitrate; 5) sodium hydroxide; 6) ammonium nitrate. AT 10 O'CLOCK. The substance, the firing of which is an endothermic reaction, is: 1) pyrite; 2) limestone; 3) dolomite; 4) zinc blende; 5) pyrites; 6) copper sulfate.

Part A A1A2A3A4A5A6A7A8A9A Part B B1B2B3B4B5B6B7B8B9B

slide 2

The purpose of the lesson

formation at the interdisciplinary level of ideas about reversible reactions, chemical equilibrium, as a dynamic state of the system, the ability to solve problems by methods of its displacement.

slide 3

Lesson objectives

Educational: to acquaint students with the concepts: reversible reactions, equilibrium, equilibrium concentrations, equilibrium constant. To study the factors influencing the shift in equilibrium.

slide 4

Developing: improve intellectual skills: highlight the main thing in the teacher's story, develop the ability to observe, compare, draw conclusions from the observations given, improve the ability to express and justify judgments, develop skills in working with chemical reagents.

slide 5

Educational: to educate an ecological culture: to show the role of balance shift in increasing the yield of a reaction product in the chemical industry and, as a result, reducing environmental pollution. To cultivate a culture of speech and communication, diligence, independence in the choice of solving problems.

slide 6

Which chemical reactions are reversible?

1. NaOH + HCl  NaCl + H2O 2. N2 + 3H2 2NH3 3. AgNO3 + NaCl  AgCl + NaNO3 4. SO3 + H2O  H2SO4 5. CH4 + 2O2 CO2 + 2H2O 6. 2SO2 + O2 2SO3 7 .HCOOH + CH3OH  HCOOCH3 + H2O

Slide 7

By direction of the process REVERSIBLE IRREVERSIBLE

Slide 8

IRREVERSIBLE REACTIONS ARE REACTIONS THAT PROCEED UNDER THESE CONDITIONS IN ONE DIRECTION ONLY. These include all exchange reactions accompanied by the formation of a precipitate, gas or a low-dissociating substance (water) and all combustion reactions.

Slide 9

Reversible reactions are reactions occurring under given conditions simultaneously in two opposite directions. Such reactions are the vast majority. In organic chemistry, the sign of reversibility is reflected in the names - antonyms of the processes * Hydrogenation - dehydrogenation * Hydration - dehydration * Polymerization - depolymerization All esterification reactions (the opposite process is called hydrolysis) and hydrolysis of proteins, esters, carbohydrates, polynucleotides are reversible. The reversibility of these processes underlies the most important property of a living organism - metabolism.

Slide 10

Equilibrium concentrations

equilibrium is dynamic, because how many molecules of the product of the direct reaction are formed per unit of time, so many of them decompose per unit of time during the reverse reaction. Under these conditions, the concentrations of all reactants remain constant. These concentrations are called equilibrium and denote them: [ H2 ], , [ HI ].

slide 11

Reversible reactions

Н2+ I2  2НI 3H2 + N2  2NH3 + Q

slide 12

Kinetic equations

According to the law of mass action, the kinetic equations have the form: Vpr \u003d k 1 s (H2) s (I2) Vob \u003d k 2 s 2 (HI)

slide 13

Slide 14

Equilibrium constant

For the reaction aA + vV  cC + dd c . [d] d K equals = ----------------------- [A] a. [B] in

slide 15

N 2 + 3 H2 2 NH3 direct reverse The state of the system in which the rate of the forward reaction is EQUAL to the rate of the reverse reaction is called chemical equilibrium graph

slide 16

STATE OF BALANCE IN NATURE Circulation of elements and substances in nature Balanced energy flows in ecosystems of different levels

Slide 17

CHATELIER PRINCIPLE

If an external influence is applied to a system in a state of equilibrium (change pressure, temperature, concentration), then the equilibrium will shift in the direction of decreasing this impact (1884)

Slide 18

Henri Louis Le Chatelier (8. 10. 1850 - 17. 09. 1936) French physical chemist and metallurgist, member of the Paris Academy of Sciences (since 1907). Born in Paris. He studied at the Polytechnic School and the Higher School of Mines in Paris. Then he was a mining engineer in Algiers and Besançon. In 1878 - 1919 professor at the Higher Mining School. In 1907 - 1925 he worked at the University of Paris. Research related to physical chemistry. He proposed an original method for determining the heat capacities of gases at high temperatures. Formulated (1884) the general law of displacement of chemical equilibrium (Le Chatelier's principle). Studied chemical processes in metallurgy. Studied the properties and methods of preparation of cements. He created a metallographic microscope and improved the methodology for studying the structure of metals and alloys. Found the conditions for the synthesis of ammonia. President of the French Chemical Society (1931). Foreign member - correspondent of the St. Petersburg Academy of Sciences (since 1913) and honorary member of the USSR Academy of Sciences (since 1926).

Slide 19

Factors affecting the shift of chemical equilibrium.

Effect of temperature change Effect of concentration change Effect of pressure change

Slide 20

1. Concentration N2 + 3 H2 Reacting substances Reaction products REACTING SUBSTANCES TO THE RIGHT WITH REACTION PRODUCTS TO THE LEFT 2 NH3

slide 21

2. Temperature endothermic reaction (- Q) exothermic reaction (+ Q) N2 + 3 H2 +Q - Q t0c equilibrium will shift to the left t0c equilibrium will shift to the right 2 NH3 + Q t0c = - Q t0c= + Q

slide 22

3. Pressure Pressure only applies to gases! N2(g) + 3 H2(g) 1V 3V 2V 4V P equilibrium will shift to the right P balance will shift to the left 2NH3(g) P - V P - V The volume of solid and liquid substances is zero

slide 23

In which direction will the equilibrium shift in a reversible process, the equation of which is 2 NO (g) + O2 (g) 2 NO2 (g) + Q, if to the right to the left to the right

slide 24

Effect of pressure change

CO2+H2O H2CO3 When the bottle cap is removed, gas evolution is observed, and the equilibrium has shifted towards the reverse reaction. With increasing pressure, the equilibrium shifts towards a smaller volume of gaseous substances H2CO3 After closing the cap of the bottle, the pressure increases, no gas evolution is observed, and the equilibrium shifts towards the direct reaction

Slide 25

Effect of concentration change

3. 3KNCS + FeCl3 Fe(CNS)3 + 3KCl thiocyanate chloride Fe (III) dark red + 30 ml H2O + 2-3 drops FeCl3 + 1-2 drops KNCS + 1-2 drops KCl 2. 1. At increase in the concentration of reogir. substances or a decrease in the concentration of the reaction product, the chemical equilibrium shifts towards the reaction products. When the concentration of the reaction products increases or the concentration of the reactants decreases, the chemical equilibrium shifts towards the starting substances.

slide 26

Effect of temperature change

  Blue color is formed in hot water In cold water 2 test tubes of starch paste Add 2 drops of J2 (C6H10O5)n + m J2[(C6H10O5)n m J2] starch blue color At elevated t, the color disappears, the equilibrium shifts to the side (endothermic) back reaction. At lower t, the color appears, the equilibrium shifts towards the (exothermic reaction) direct reaction.

Slide 27

As you know, the air contains 21% oxygen (by mass). Such an amount is necessary to maintain natural equilibrium: 3O2 (g)  2O3 (g) - Q. Classify this reaction. How important is ozone to planet Earth? Using Le Chatelier's principle, suggest the conditions under which the equilibrium will shift towards the formation of ozone.

Slide 28

Le Chatelier's principle is widely used in chemical engineering to improve product yield. Is the process of oxygen transfer in the body consistent with Le Chatelier's principle (justify your answer)? Hb + O2 HbO2

Slide 29

Tests

I Reproductive level: tests with alternative answers, in which the subject must answer yes or no. 1. Is the combustion reaction of phosphorus a reversible reaction? a) yes b) no 2. Is the decomposition reaction of calcium carbonate a reversible reaction? a) yes b) no

slide 30

Slide 31

tests

* Tests with the choice of one correct answer 6. In which system, when the pressure increases, the chemical equilibrium will shift to the right? 1) 2HI(g)↔H2(g)+I2(g) 2) N2 + O2↔ 2 NO 3) C3 H6(g)+H2(g)↔С3 H8(g) 4) H2(g)+F2 (g)↔2HF(g)

slide 32

Tests

Tests with multiple choice of the correct answer, during which the subject must choose 2-3 correct answers, or match 2 proposed conditions when choosing an answer.

Slide 33

tests

16. Indicate the correct judgment: A) in reversible processes, the rate of the direct reaction in the period from the beginning of the reaction to reaching equilibrium decreases; B) in reversible processes, the rate of the direct reaction after reaching equilibrium is zero. 1) only A is true 2) only B is true 3) both judgments are correct 4) both judgments are wrong

slide 34

Reflection

I worked actively / passively at the lesson I am satisfied / dissatisfied with my work at the lesson The lesson seemed short / long for me During the lesson I was tired / not tired My mood became better / became worse The material of the lesson was useful / useless understandable / not understandable easy / difficult Homework interesting / not interesting

View all slides