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UNIT 2 Chapter 4: Developing Chemical Equations Chapter 5:Classifying Chemical Reactions Chapter 6:Acids and Bases Chemical Reactions.

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Presentation on theme: "UNIT 2 Chapter 4: Developing Chemical Equations Chapter 5:Classifying Chemical Reactions Chapter 6:Acids and Bases Chemical Reactions."— Presentation transcript:

1 UNIT 2 Chapter 4: Developing Chemical Equations Chapter 5:Classifying Chemical Reactions Chapter 6:Acids and Bases Chemical Reactions

2 CHAPTER 5 Classifying Chemical Reactions In this chapter, you will: describe evidence of chemical reactions identify reactants and products of the four reaction types discuss chemical reactions associated with environmental concerns In this chapter, you will: describe evidence of chemical reactions identify reactants and products of the four reaction types discuss chemical reactions associated with environmental concerns Copyright © 2010 McGraw-Hill Ryerson Ltd.

3 Introductory Activity 5.1 : Foiled Again! With a reaction such as the one shown on page 177, answer the following questions. What changes do you observe? Why is this a chemical change? What were the reactants and products? What happens to the mass of reactants and products during the reaction? (Page 177)

4 Copyright © 2010 McGraw-Hill Ryerson Ltd. 5.1 Synthesis and Decomposition Reactions Metal corrosion led to the damage shown in the picture below. The chemical reaction that occurred is illustrated by the following balanced chemical equation. 4Fe(s) + 3O 2 (g) 2Fe 2 O 3 (s) (Page 179)

5 Copyright © 2010 McGraw-Hill Ryerson Ltd. Evidence of Chemical Change The following images illustrate some examples of evidence that a chemical change has occurred. Gas formation - usually observed as bubbles Precipitate formation – an insoluble solid formed during a reaction Colour change – a new colour being produced Energy production – the production of light or heat by a reaction Difficult to Reverse – reaction cannot occur in the opposite direction (Page 180)

6 Copyright © 2010 McGraw-Hill Ryerson Ltd. Synthesis Reactions A synthesis reaction is a chemical reaction in which two or more reactants combine to produce a new product. Examples of synthesis reactions The shuttle blast off 2H 2 (l) + O 2 (l) 2H 2 O(g) The Haber process to produce ammonia N 2 (g) + 3H 2 (g) 2NH 3 (g) The production of smog N 2 (g) + O 2 (g) 2NO 2 (g) and 2NO(g) + O 2 (g) 2NO 2 (g) (Pages )

7 Copyright © 2010 McGraw-Hill Ryerson Ltd. Precipitation Reactions

8 Copyright © 2010 McGraw-Hill Ryerson Ltd. Precipitation Reactions Click the Start buttons to review your understanding of synthesis reactions that produce precipitate. (Page 180)

9 Copyright © 2010 McGraw-Hill Ryerson Ltd. Synthesis Reactions Review your understanding of synthesis reactions. (Page 181)

10 Copyright © 2010 McGraw-Hill Ryerson Ltd. Decomposition Reactions A decomposition reaction is a chemical reaction in which a compound breaks down (decomposes) into two or more simpler compounds or elements. Examples of decomposition reactions The electrolysis of water 2H 2 O(l) 2H 2 (g) + O 2 (g) A TNT Explosion 2C 7 H 5 N 3 O 6 (s) 3N 2 (g) + 5H 2 O(g) + 7CO(g) + 7C(s) Decomposition of sodium azide 2NaN 3 (s) 3N 2 (g) + 2Na(s) (Pages )

11 Copyright © 2010 McGraw-Hill Ryerson Ltd. Decomposition Reactions Review your understanding of decomposition reactions. (Pages )

12 Copyright © 2010 McGraw-Hill Ryerson Ltd. Section 5.1 Review Concepts to be reviewed: evidence of a chemical change synthesis reactions (chemical equation and examples) decomposition reactions (chemical equation and examples) (Page 189)

13 Copyright © 2010 McGraw-Hill Ryerson Ltd. 5.2 Displacement Reactions Many industrial processes, such as the one used to isolate nickel from the deposits found around Sudbury, rely on a series of chemical reactions that include the displacement of one element by another to form a new compound. (Page 190)

14 Producing copper (Cu) metal Mg(s) + CuSO 4 (aq) MgSO 4 (aq) + Cu (s) Copyright © 2010 McGraw-Hill Ryerson Ltd. Single Displacement Reactions A single displacement reaction is a chemical reaction in which one element (a reactive metal or non- metal) takes the place of an element in a compound to produce another element and another compound. A + BC AC + B Where A is a metal A + BC BA + C Where A is a non-metal Examples of single displacement reactions Displacing silver (Ag) from silver nitrate (AgNO 3 ) Cu(s) + 2AgNO 3 (aq) Cu(NO 3 ) 2 (aq) + 2Ag(s) Producing zinc chloride (ZnCl 2 ) and hydrogen gas (H 2 ) Zn(s) + 2HCl(aq) ZnCl 2 (aq) + H 2 (g) (Page 191)

15 Copyright © 2010 McGraw-Hill Ryerson Ltd. Activity Series The activity series is a list of elements organized according to their chemical reactivity. The most reactive element appears on the top, and the least reactive appears at the bottom. Metals higher up on the activity series list will replace metals lower on the list during a single displacement reaction. Remember! Metals can only replace other metals in a reaction, and non- metals can only replace other non-metals. (Page 192)

16 Copyright © 2010 McGraw-Hill Ryerson Ltd. Single Displacement Reactions Review your understanding of single displacement reactions. (Pages )

17 Copyright © 2010 McGraw-Hill Ryerson Ltd. Double Displacement Reactions A double displacement reaction is a chemical reaction in which the positive ions of two different compounds exchange places, resulting in the formation of two new compounds – one of which may be a precipitate. Producing silver chromate (AgCrO 4 (s) ) (the red precipitate) and potassium nitrate (2KNO 3 (aq)) (Pages )

18 Copyright © 2010 McGraw-Hill Ryerson Ltd. Double Displacement Reactions Review your understanding of double displacement reactions. (Pages )

19 Copyright © 2010 McGraw-Hill Ryerson Ltd. Chemical Reactions and Food Preservation Sulfur dioxide (SO 2 ) is used to preserve the colour of dried fruit. A double displacement reaction followed by a decomposition reaction releases the sulfur dioxide gas required for the process. The double replacement reaction Na 2 SO 3 (aq) + 2HCl(aq) 2NaCl (aq) + H 2 SO 3 (aq) The decomposition reaction H 2 SO 3 (aq) H 2 O(l) + SO 2 (g) (Page 197)

20 Copyright © 2010 McGraw-Hill Ryerson Ltd. Summary of Reaction Types (Page 197)

21 Copyright © 2010 McGraw-Hill Ryerson Ltd. Summary of Reaction Types One additional type of chemical reaction that you will learn about in future studies is a combustion reaction. These reactions always involve a fuel reacting with oxygen to release energy. Carbon dioxide and water are also produced by the reaction. (Page 197)

22 Copyright © 2010 McGraw-Hill Ryerson Ltd. Section 5.2 Review Concepts to be reviewed: single displacement reactions the activity series of elements double displacement reactions (Page 198)

23 Copyright © 2010 McGraw-Hill Ryerson Ltd. 5.3 Reactions and Environmental Issues Although chemical reactions can cause environmental issues, they can also be used to help solve environmental challenges. (Page 199)

24 2C 8 H 18 (l) + 25O 2 (g) 16CO 2 (g) + 18H 2 O(g) Copyright © 2010 McGraw-Hill Ryerson Ltd. Treating Car Exhaust The complete combustion of gasoline in a cars engine is represented by the following chemical equation. Incomplete combustion can result in carbon (C) (soot), carbon monoxide (CO), and nitrogen oxides (NO 2 and NO 3 ) entering the air. A catalytic converter installed in a vehicles exhaust system can help reduce the amounts of these pollutants in the atmosphere. (Pages )

25 Copyright © 2010 McGraw-Hill Ryerson Ltd. Recovering Gold using Cyanide and Zinc Cyanide ions (CN - ) are used to extract gold from rock or ore. 4Au(s) + 8NaCN(aq) + O 2 (g) + 2H 2 O (l) 4Na[Au(CN) 2 ](aq) + 4NaOH(aq) Leaching, a technique that removes gold by dissolving it in an aqueous solution, is used to drain the gold away from the ore. Zinc (Zn) can then be used in a single displacement reaction to displace the gold from the solution. 2Na[Au(CN) 2 ](aq) + Zn(s) 2NaCN(aq) + Zn(CN) 2 (aq) + 2Au(s) (Pages )

26 Copyright © 2010 McGraw-Hill Ryerson Ltd. Cleaning and Disinfecting Pools A variety of compounds containing chlorine (Cl) are used to prevent the growth of bacteria and other organisms in the water in swimming pools and hot tubs. Care must be taken when using these chemicals to ensure that they are effective in disinfecting the water but remain safe for the users. (Page 203)

27 Copyright © 2010 McGraw-Hill Ryerson Ltd. Hazards in the Home Precautions must be taken when using household chemicals. When mixed, reactions could occur that might be detrimental to the users health. (Pages )

28 Copyright © 2010 McGraw-Hill Ryerson Ltd. Bleach and Ammonia – A Toxic Combination The mixing of bleach (NaClO) (a compound containing chlorine), and ammonia (NH 3 ) can have dire consequences. Two other ammonia and bleach reactions produce toxic compounds called chloramines (NCl 3 (g) and NH 2 Cl(g)). 2NH 3 (aq) + 2NaClO(aq) 2NaONH 3 (aq) + Cl 2 (g) Toxic chlorine gas (Cl 2 ) is produced in this reaction. NH 3 (aq) + 3NaClO(aq) 3NaOH(aq) + NCl 3 (g) NH 3 (aq) + NaClO(aq) NaOH(aq) + NH 2 Cl(g) += (Page 205)

29 Copyright © 2010 McGraw-Hill Ryerson Ltd. Chemical Safety Be familiar with the WHMIS and HHPS symbols that identify the hazards associated with the handling and use of chemicals at home and in the workplace. Hazardous Household Product Symbols (HHPS) Workplace Hazardous Materials Information System (WHMIS) (Page 204)

30 Copyright © 2010 McGraw-Hill Ryerson Ltd. Section 5.3 Review Concepts to be reviewed: the use of catalytic converters to help combat exhaust pollutants the chemical reactions involved in gold extraction the hazards involved in the use and handling of household chemicals safe practices for the handling and use of chemicals familiarity with WHMIS and HPPS symbols and warnings (Page 206)


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