We think you have liked this presentation. If you wish to download it, please recommend it to your friends in any social system. Share buttons are a little bit lower. Thank you!
Presentation is loading. Please wait.
Published byCarlo Barden
Modified about 1 year ago
© Boardworks Ltd of 39
© Boardworks Ltd of 39
3 of 39© Boardworks Ltd 2007 Irreversible reactions Most chemical reactions are considered irreversible – the products that are made cannot readily be changed back into their reactants. For example, when wood burns it is impossible to turn it back into unburnt wood again! Similarly, when magnesium reacts with hydrochloric acid to form magnesium chloride and hydrogen, it is not easy to reverse the reaction and obtain the magnesium.
4 of 39© Boardworks Ltd 2007 What are reversible reactions? Reversible reactions occur when the backwards reaction (products reactants) takes place relatively easily under certain conditions. The products turn back into the reactants. + ABCD + (reactants)(products) For example, during a reversible reaction reactants A and B react to make products C and D. However, products C and D can also undergo the reverse reaction, and react together to form reactants A and B.
5 of 39© Boardworks Ltd 2007 Reversible and irreversible reactions What kind of reactions are reversible and irreversible?
6 of 39© Boardworks Ltd 2007 Hb + 4O 2 Hb.4O 2 Reversible biochemical reactions Many biochemical reactions (those that take place inside organisms) are reversible. There are also some very important industrial reactions, like the Haber process, that are reversible. For example, in the lungs, oxygen binds to haemoglobin (Hb) in red blood cells to create oxyhaemoglobin. When the red blood cells are transported to tissues, the oxyhaemoglobin dissociates back to haemoglobin and oxygen.
7 of 39© Boardworks Ltd 2007 Heating copper sulfate
8 of 39© Boardworks Ltd 2007 Heating ammonium chloride An ammonium salt can be made by reacting ammonia with an acid. Some of the salt will decompose back into the reactants when heated. ammonium chloride ammonia + hydrogen chloride NH 3 (g)NH 4 Cl (s) HCl (g) + NH 4 Cl decomposes back into NH 3 and HCl gases when heated NH 4 Cl reforms in the cooler part of the test tube
9 of 39© Boardworks Ltd 2007 Reversible or irreversible?
© Boardworks Ltd of 39
11 of 39© Boardworks Ltd 2007 What is dynamic equilibrium? In some reversible reactions, the forward and backward reactions largely occur in the same conditions and at the same rate. These reactions are said to be in dynamic equilibrium – there is no overall change in the amount of products and reactants, even though the reactions are ongoing. Dynamic equilibrium can only take place in a closed system, otherwise the products would escape. reactant A + productreactant B
12 of 39© Boardworks Ltd 2007 What happens in dynamic equilibrium? What is special about the forward and backward reactions at dynamic equilibrium?
13 of 39© Boardworks Ltd 2007 Setting dynamic equilibrium The position of dynamic equilibrium is not always at a half-way point, i.e. when there are equal amounts of products and reactants. It may be at a position where there are mainly reactants with a little product, or vice versa. The position of equilibrium is influenced by two main factors: temperature concentration (or pressure for reactions involving gases) Adding a catalyst speeds up the time it takes to reach equilibrium, but does not change the position of equilibrium.
14 of 39© Boardworks Ltd 2007 True or false?
© Boardworks Ltd of 39
16 of 39© Boardworks Ltd 2007 Opposing change Whenever a change is made to a reversible reaction in dynamic equilibrium, the equilibrium will shift to try and oppose the change. Increasing the temperature shifts the equilibrium in the direction that takes in heat. Increasing the concentration of a substance shifts the equilibrium in the direction that produces less of that substance. Increasing the pressure shifts the equilibrium in the direction that produces less gas. Temperature Concentration Pressure Condition Effect
17 of 39© Boardworks Ltd 2007 Exothermic and endothermic reactions All reactions are exothermic (give out heat) in one direction and endothermic (take in heat) in the other. If the temperature is increased: If the temperature is decreased: equilibrium shifts to decrease the temperature equilibrium shifts in the endothermic direction equilibrium shifts to increase the temperature equilibrium shifts in the exothermic direction
18 of 39© Boardworks Ltd 2007 Opposing changes in temperature Nitrogen dioxide is in constant equilibrium with dinitrogen tetroxide. The forward reaction is exothermic and the backwards reaction is endothermic. What will happen if the temperature is increased? The equilibrium will shift to decrease the temperature, i.e. to the left (endothermic). If the temperature is decreased, more N 2 O 4 will be produced. N 2 O 4 (g) 2NO 2 (g) nitrogen dioxidedinitrogen tetroxide More NO 2 will be produced.
19 of 39© Boardworks Ltd 2007 Concentration and equilibrium Changing the concentration of a substance affects the equilibrium of reversible reactions involving solutions. increasing the concentration of substance A equilibrium shifts to decrease the amount of substance A = decreasing the concentration of substance A equilibrium shifts to increase the amount of substance A =
20 of 39© Boardworks Ltd 2007 Opposing changes in concentration (1) Bismuth chloride reacts with water to produce a white precipitate of bismuth oxychloride and hydrochloric acid. What will happen if more H 2 O is added? If H 2 O is removed, more BiCl 3 and H 2 O will be produced. The equilibrium will shift to decrease the amount of water, i.e. to the right. bismuth oxychloride bismuth chloride water hydrochloric acid ++ BiOCl (s)BiCl 3 (aq)H 2 O (l)2HCl (aq) ++ More BiOCl and HCl will be produced.
21 of 39© Boardworks Ltd 2007 Opposing changes in concentration (2) It will become more yellow. Chlorine gas reacts with iodine chloride to produce iodine trichloride. What effect will adding more Cl 2 have on the colour of the mixture? What effect will removing Cl 2 have on the colour of the mixture? It will become more brown. iodine trichloride chlorine iodine chloride + ICl 3 (s)Cl 2 (g) + ICl (l) pale greenbrownyellow
22 of 39© Boardworks Ltd 2007 Pressure and equilibrium Changing the pressure has an effect on the equilibrium of reversible reactions involving gases. If the pressure is increased: equilibrium shifts to decrease the pressure equilibrium shifts in the direction of fewest molecules If the pressure is decreased: equilibrium shifts to increase the pressure equilibrium shifts in the direction of most molecules
23 of 39© Boardworks Ltd 2007 Opposing changes in pressure Nitrogen dioxide is in constant equilibrium with dinitrogen tetroxide. Two molecules of nitrogen dioxide react to form one molecule of dinitrogen tetroxide. If the pressure is decreased, more NO 2 will be produced. N 2 O 4 (g) 2NO 2 (g) dinitrogen tetroxide nitrogen dioxide The equilibrium will shift to reduce the number of molecules, i.e. to the right (only 1 molecule). What will happen if the pressure is increased? More N 2 O 4 will be produced.
24 of 39© Boardworks Ltd 2007 Dynamic equilibrium and change
© Boardworks Ltd of 39
26 of 39© Boardworks Ltd 2007 What is ammonia? It is made industrially by reacting nitrogen with hydrogen in the Haber process. It is a reversible reaction, so it never goes to completion. hydrogennitrogen + ammonia N 2 (g)3H 2 (g)2NH 3 (g) + Ammonia is an important compound in the manufacture of fertilizer and other chemicals such as cleaning fluids and floor waxes. Why is this a problem for companies making ammonia?
27 of 39© Boardworks Ltd 2007 The Haber process
28 of 39© Boardworks Ltd 2007 What is yield? The amount of product made in a reaction is called the yield and is usually expressed as a percentage. ammonia yield (%) pressure (atm) The yield of ammonia produced by the Haber process depends on the temperature and pressure of the reaction.
29 of 39© Boardworks Ltd 2007 What is the Haber compromise? In practice, though, these conditions are not used. Why? The highest yield of ammonia is theoretically produced by using a low temperature and a high pressure. A compromise is reached to make an acceptable yield in a reasonable timeframe while keeping costs down. Lowering the temperature slows down the rate of reaction. This means it takes longer for ammonia to be produced. Increasing the pressure means stronger, more expensive equipment is needed. This increases the cost of producing the ammonia.
30 of 39© Boardworks Ltd 2007 Temperature, pressure and yield
31 of 39© Boardworks Ltd 2007 Changing the yield of ammonia
32 of 39© Boardworks Ltd 2007 The Haber compromise To produce a high yield of ammonia, but with a fast rate of reaction and without the need for overly expensive equipment, the Haber process is carried out at 450 °C and 200 atmospheres. The most important factor in deciding what conditions to use is therefore not yield, but total cost. raw materials equipment energy wages What costs are involved in the industrial production of ammonia?
33 of 39© Boardworks Ltd 2007 Maximizing productivity What else can be done to maximise productivity in the manufacture of ammonia? An iron catalyst is used to increase the rate of reaction. It speeds up both the forward and backward reaction, so the position of equilibrium is not affected. The ammonia is cooled, liquefied and then removed as it is produced. This causes the equilibrium to shift to the right to produce more ammonia. Unreacted nitrogen and hydrogen are recycled and given another chance to react.
34 of 39© Boardworks Ltd 2007 Temperature, pressure and yield
35 of 39© Boardworks Ltd 2007 Stages of the Haber process
© Boardworks Ltd of 39
37 of 39© Boardworks Ltd 2007 Glossary closed system – A system in which reactants and products cannot be added or removed once the reaction has begun. dynamic – An equilibrium in which the forward and backward reactions take place at the same rate, so no overall change takes place. Haber process – The industrial-scale process for making ammonia from nitrogen and hydrogen. irreversible – A reaction that is impossible or very difficult to reverse. reversible – A reaction in which the product(s) can be turned back into the reactants. yield – The amount of product obtained from a reaction, usually expressed as a percentage.
38 of 39© Boardworks Ltd 2007 Anagrams
39 of 39© Boardworks Ltd 2007 Multiple-choice quiz
© Boardworks Ltd of of 10© Boardworks Ltd 2007 Opposing change Whenever a change is made to a reversible reaction in dynamic equilibrium,
HABER PROCESS. What is ammonia? It is made industrially by reacting nitrogen with hydrogen in the Haber process. It is a reversible reaction, so it never.
Reversible Reactions and Equilibrium. Mg + 2HCl MgCl 2 + H 2 Irreversible reactions Most Chemical reactions are considered irreversible in that products.
© Boardworks Ltd 2001 Reversible Reactions and Equilibrium.
Equilibrium. Write down on separate post-it notes what you think each of the following terms means. Open system Closed system Reversible reaction Equilibrium.
00:33 Syllabus/Unit: code: C2 Chemical Resources Lesson number: 5 Lesson Title: Manufacturing Chemicals - Ammonia Learning OutcomesHow I didTargets Learning.
© Boardworks Ltd of of 39© Boardworks Ltd 2007 Irreversible reactions Most chemical reactions are considered irreversible – the products that.
1 of 29© Boardworks Ltd Dynamic Equilibria Learning Objectives: 1.Understand that most reactions are reversible. 2.Understand chemical equilibrium.
Approaching Equilibrium Lesson 1. Mg + 2HCl MgCl 2 + H 2 Irreversible reactions Most Chemical reactions are considered irreversible in that products.
Chemical Equilibrium. Equilibrium – A state of balance Static Equilibrium – When a meter stick is balanced in the middle neither end is moving this is.
The Haber Process Reversible Reactions and Dynamic Equilibrium.
Noadswood Science, To be able to explain and give examples of reversible reactions Tuesday, September 08, 2015 Reversible Reactions A B A B These.
Unusual Reactions L.O: To understand what happens in some unusual chemical reactions.
1 of 33© Boardworks Ltd of 33© Boardworks Ltd 2010.
Chemistry Unit 3 (C7) Revision Slides. Hydrocarbons in crude oil Many compounds in crude oil only contain the elements carbon and hydrogen. They are called.
05/05/ Do Chemical Reactions Always Release Energy? Heolddu Comprehensive School.
The Haber Process: Making Ammonia L.O: To understand the production of ammonia through the haber process.
Write down everything you can think of about this reaction: Nitrogen + Hydrogen ⇌ Ammonia ⇌ reaction is reversible rate of forward reaction = rate of reverse.
Introduction to Chemical Equilibrium Chapter 15 CHEM 160.
Unit 3 Equilibrium. HIGHER CHEMISTRY REVISION. Unit 3 :- Equilibrium 1. If both potassium iodide solution, KI(aq), and liquid chloroform, CHCl 3 (l),
11 IB Topic 7: Equilibrium 7.1: Dynamic equilibrium 7.1.1Outline the characteristics of chemical and physical systems in a state of equilibrium.
1 Chemical Equilibrium You learned when we studied mechanisms that some rxns are reversible or equilibrium rxns The double arrow is used to show this.
Chemical Equilibrium Section 18-1 Pp Equilibrium is… Equilibrium is not static Opposing processes occur at the same time and at the same rate.
Reversible Reactions – Part II. Le Chateliers Principle For a system at equilibrium, an alteration in the conditions will cause the state of balance to.
Chemical Equilibrium A Balancing Act. During a game, players enter and leave... But there are always the same number of players on field.
Section 2: Shifting Equilibrium. Objectives Discuss the factors that disturb equilibrium. Discuss conditions under which reactions go to completion. Describe.
IGCSE CHEMISTRY SECTION 4 LESSON 4. Content The iGCSE Chemistry course Section 1 Principles of Chemistry Section 2 Chemistry of the Elements Section 3.
Section 1 Reversible Reactions and Equilibrium Completion Reactions and Reversible Reactions Do all reactants change into products during a reaction?
The Haber Process. The Haber process is used to gain ammonia Ammonia is used for: – Plant Fertilliser – Hair Dye.
1 of 36© Boardworks Ltd of 36© Boardworks Ltd 2009.
Reaction Rates Chapter 18 CP Chemistry Reactions can be… FAST! Liquid hydrogen and oxygen reacting to launch a shuttle.
Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Completion Reactions and Reversible Reactions If enough oxygen gas.
Equilibrium. Non reversible reactions Some chemical and physical reactions occur until one or all the reactants are used up Example 1 Evaporation of water.
Prentice Hall © 2003Chapter 15 Chapter 15 Chemical Equilibrium CHEMISTRY The Central Science 9th Edition David P. White.
1 Chemical Equilibrium Chapter 17 (Honors) SAVE PAPER AND INK!!! When you print out the notes on PowerPoint, print "Handouts" instead of "Slides" in the.
AQA Module C2 Reversible Reactions & The Haber Process.
Equilibrium Unit 10. Reaction Dynamics If the products of a reaction are removed from the system as they are made, then a chemical reaction will proceed.
EQUILIBRIUM TIER 4 Apply LeChatelier’s principle to predict the qualitative effects of changes of temperature, pressure and concentration on the position.
1.Ammonia (alkaline) and nitric acid react together in a neutralisation reaction 2.The fertiliser ammonium nitrate is produced Making Fertilisers Making.
HIGHER CHEMISTRY REVISION. Unit 3 :- Equilibrium 1. If both potassium iodide solution, KI(aq), and liquid chloroform, CHCl 3 (l), are added to a test tube.
Industrial chemistry Kazem.R.Abdollah (Asiaban) The Haber Process & The Ostwald Process 1.
1 of 39© Boardworks Ltd of 39 © Boardworks Ltd of 39 What does rate of reaction mean? The speed of different chemical reactions varies.
THE POSITION OF EQUILIBRIUM Section 7.2. THE EQUILIBRIUM CONSTANT The position of equilibrium for a particular reversible reaction can be defined by a.
Le Chatelier’s Principle. When a chemical system at equilibrium is disturbed by a change in a property of the system, the system always appears to react.
Chemical Equilibrium. Reversible Reactions Most chemical reactions are reversible. What does this mean? The products of a chemical reaction, under certain.
Equilibrium A state in which opposing processes of a system are occurring at the same rate. 1.Physical (a) Saturated Solution – dissolution and crystallization.
1 Le Châtelier. 2 Standard Know how to use Le Châtelier’s principle to predict the effect of changes in concentration, pressure, and temperature. Know.
EQUILIBRIUM 2 REACTION YIELDS. Equilibrium Very few reactions proceed unhindered to completion. Some begin reversing as soon as products are present.
© 2017 SlidePlayer.com Inc. All rights reserved.