1. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 1 Chapter 6 Chemical Reactions 6.1 Chemical Changes 6.2 Chemical Equations 6.3 Balancing a Chemical Equation

2. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 2  The physical properties of a substance are the characteristics we can observe or measure without changing the substance. Physical Properties

3. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 3 In a physical change, The identity and composition of the substance do not change. The state can change or the material can be torn into smaller pieces. In a chemical change, New substances form with different compositions and properties. A chemical reaction takes place. Physical and Chemical Change

4. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 4 Physical and Chemical Change

5. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 5 Some Examples of Chemical and Physical Changes

6. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 6 Classify each of the following as a 1) physical change or 2) chemical change A. ____ Burning a candle. B. ____ Ice melting on the street. C. ____ Toasting a marshmallow. D. ____ Cutting a pizza. E. ____ Polishing a silver bowl. Learning Check

7. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 7 Classify each of the following as a 1) physical change or 2) chemical change A. 2 Burning a candle. B. 1 Ice melting on the street. C. 2 Toasting a marshmallow. D. 1 Cutting a pizza. E. 2 Polishing a silver bowl. Solution

8. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 8 Chemical Reaction In a chemical reaction, a chemical change produces one or more new substances. During a reaction, old bonds are broken and new bonds are formed.

9. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 9  In a chemical reaction, atoms in the reactants are rearranged to form one or more different substances.  In this reaction, Fe and O 2 react to form rust (Fe 2 O 3 ). 4Fe + 3O 2 2Fe 2 O 3 Chemical Reaction

10. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 10  A chemical equation  Shows the chemical formulas of the reactants to the left of an arrow and the products on the right. Reactants Products MgO + CCO + Mg  Can be read in words. “Magnesium oxide reacts with carbon to form carbon monoxide and magnesium.” Writing a Chemical Equation

11. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 11 Symbols Used in Equations Symbols used in equations show the states of the reactants and products and the reaction conditions.

12. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 12 4 NH 3 + 5 O 2 4 NO + 6 H 2 O Four molecules of NH 3 react with five molecules of O 2 to produce four molecules of NO and six molecules of H 2 O. or Four moles of NH 3 react with 5 moles of O 2 to produce four moles of NO and six moles of H 2 O. Quantities in A Chemical Reaction

13. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 13 In any ordinary chemical reaction, matter is not created nor destroyed. + + H 2 + Cl 2 2 HCl Total atoms=Total atoms 2 H, 2 Cl 2H, 2 Cl Total Mass=Total Mass 2(1.0) + 2(35.5)2(36.5) 73.0 g=73.0 g Law of Conservation of Mass

14. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 14 Balancing a Chemical Equation A chemical equation is balanced when there are the same numbers of each type of atom on both sides of the equation. Al + S Al 2 S 3 Not Balanced 2Al + 3S Al 2 S 3 Balanced

15. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 15  To balance an equation, place coefficients in front of the appropriate formulas. 4 NH 3 + 5 O 2 4 NO + 6 H 2 O  Check the balance by counting the atoms of each element in the reactants and the products. 4 N (4 x 1N) = 4 N (4 x 1N) 12 H (4 x 3H) = 12 H (6 x 2H) 10 O (5 x 2O)= 10 O(4O + 6O) Using Coefficients to Balance

16. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 16 Balance one element at a time. Use only coefficients to balance. Fe 3 O 4 + H 2 Fe + H 2 O Fe:Fe 3 O 4 + H 2 3Fe + H 2 O O:Fe 3 O 4 + H 2 3Fe + 4H 2 O H: Fe 3 O 4 + 4H 2 3Fe + 4H 2 O Steps in Balancing an Equation

17. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 17 Check the balance of atoms in the following: Fe 3 O 4 + 4 H 2 3 Fe + 4 H 2 O A. Number of H atoms in products. 1) 22) 43) 8 B. Number of O atoms in reactants. 1) 22) 43) 8 C. Number of Fe atoms in reactants. 1) 12) 33) 4 Learning Check

18. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 18 Fe 3 O 4 + 4 H 2 3 Fe + 4 H 2 O A. Number of H atoms in products. 3) 8 (4H 2 O) B. Number of O atoms in reactants. 2) 4 (Fe 3 O 4 ) C. Number of Fe atoms in reactants. 2) 3 (Fe 3 O 4 ) Solution

19. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 19 Balancing with Polyatomic Ions Polyatomic ions can be balanced as a unit when they appear on both sides. Pb(NO 3 ) 2 + NaCl NaNO 3 + PbCl 2 Balance NO 3 - as a unit Pb(NO 3 ) 2 + NaCl 2NaNO 3 + PbCl 2 2 NO 3 – = 2 NO 3 – Balance Na (or Cl) Pb(NO 3 ) 2 + 2NaCl 2NaNO 3 + PbCl 2 2Na + = 2Na + 2Cl – = 2Cl –

20. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 20 Balance each equation. The coefficients in the answers are read from left to right. A. __Mg + __N 2 __Mg 3 N 2 1) 1, 3, 2 2) 3, 1, 2 3) 3, 1, 1 B.__Al + __Cl 2 __AlCl 3 1) 3, 3, 22) 1, 3, 1 3) 2, 3, 2 Learning Check

21. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 21 A. 3) 3, 1, 1 3 Mg + 1 N 2 1 Mg 3 N 2 B. 3) 2, 3, 2 2 Al + 3 Cl 2 2 AlCl 3 Solution

22. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 22 A. __Fe 2 O 3 + __C __Fe + __CO 2 1) 2, 3, 2,3 2) 2, 3, 4, 3 3) 1, 1, 2, 3 B. __Al + __FeO __Fe + __Al 2 O 3 1) 2, 3, 3, 1 2) 2, 1, 1, 1 3) 3, 3, 3, 1 C. __Al + __H 2 SO 4 __Al 2 (SO 4 ) 3 + __H 2 1) 3, 2, 1, 2 2) 2, 3, 1, 3 3) 2, 3, 2, 3 Learning Check

23. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 23 A. 2) 2, 3, 4, 3 2 Fe 2 O 3 + 3 C 4 Fe + 3 CO 2 B. 1) 2, 3, 3, 1 2 Al + 3 FeO 3 Fe + 1 Al 2 O 3 C. 2) 2, 3, 1, 3 2 Al + 3 H 2 SO 4 1 Al 2 (SO 4 ) 3 + 3 H 2 Solution

24. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 24 6.4 Types of Reactions Chapter 6 Chemical Reactions

25. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 25 Chemical reactions are classified into general types:  Combination  Decomposition  Single Replacement  Double Replacement  Combustion Types of Reactions

26. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 26 In a combination reaction, two or more elements or simple compounds combine to form one product. A + B AB Examples H 2 + Cl 2 2HCl 2S + 3O 2 2SO 3 4Fe + 3O 2 2Fe 2 O 3 Combination Reactions

27. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 27 In a combination reaction, magnesium and oxygen react to form magnesium oxide. 2Mg + O 2 2MgO Combination Reactions Mg O2O2 MgO

28. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 28 In a decomposition reaction, one substance is broken down (split) into two or more simpler substances. ABA + B 2HgO2Hg + O 2 2KClO 3 2KCl + 3 O 2 Decomposition Reactions

29. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 29 Classify the following reactions as 1) combination or 2) decomposition: ___A. H 2 + Br 2 2HBr ___B. Al 2 (CO 3 ) 3 Al 2 O 3 + 3CO 2 ___C. 4 Al + 3C Al 4 C 3 Learning Check

30. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 30 Classify the following reactions as 1) combination or 2) decomposition: 1 A. H 2 + Br 2 2HBr 2 B. Al 2 (CO 3 ) 3 Al 2 O 3 + 3CO 2 1 C. 4 Al + 3C Al 4 C 3 Solution

31. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 31  In a single replacement, one element takes the place of an element in a reacting compound. A + BC AC + B Zn(s) + HCl(aq) ZnCl 2 (aq) + H 2 (g) Single Replacement Zn HCl H2H2 ZnCl 2

32. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 32 In a double replacement, the positive ions in the reacting compounds switch places. AB + CD AD + CB AgNO 3 + NaCl AgCl + NaNO 3 ZnS + 2HCl ZnCl 2 + H 2 S Double Replacement

33. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 33 Example of a Double Replacement When solutions of sodium sulfate and barium chloride are mixed, solid BaSO 4 is produced. BaCl 2 + Na 2 SO 4 BaSO 4 + 2NaCl BaSO 4

34. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 34 Classify each of the following reactions as a 1) single replacement or 2) double replacement __A. 2Al + 3H 2 SO 4 Al 2 (SO 4 ) 3 + 3H 2 __B. Na 2 SO 4 + 2AgNO 3 Ag 2 SO 4 + 2NaNO 3 __C. 3C + Fe 2 O 3 2Fe + 3CO Learning Check

35. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 35 Classify each of the following reactions as a 1) single replacement or 2) double replacement 1 A. 2Al + 3H 2 SO 4 Al 2 (SO 4 ) 3 + 3H 2 2 B. Na 2 SO 4 + 2AgNO 3 Ag 2 SO 4 + 2NaNO 3 1 C. 3C + Fe 2 O 3 2Fe + 3CO Solution

36. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 36 In a combustion reaction, a reactant often containing carbon reacts with oxygen O 2. C + O 2 CO 2 CH 4 + 2O 2 CO 2 + 2H 2 O C 3 H 8 + 5O 2 3CO 2 + 4H 2 O Many combustion reactions utilize fuels that are burned in oxygen to produce CO 2, H 2 O, and energy. Combustion

37. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 37 Balance the combustion equation: ___C 5 H 12 + ___O 2 ___CO 2 + ___H 2 O Learning Check

38. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 38 Balance the combustion equation: 1 C 5 H 12 + 8 O 2 5 CO 2 + 6 H 2 O Solution

39. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 39 Summary of Reaction Types

40. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 40 Learning Check Identify each reaction as 1) combination 2) decomposition 3) combustion 4) single replacement 5) double replacement A. 3Ba + N 2 Ba 3 N 2 B. 2Ag + H 2 S Ag 2 S + H 2 C. SiO 2 + 4HF SiF 4 + 2H 2 O D. PbCl 2 + K 2 SO 4 2KCl + PbSO 4 E. K 2 CO 3 K 2 O + CO 2 F. C 2 H 4 + 3O 2 2CO 2 + 2H 2 O

41. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 41 Solution Identify each reaction as 1) combination 2) decomposition 3) combustion 4) single replacement 5) double replacement 1 A. 3Ba + N 2 Ba 3 N 2 4 B. 2Ag + H 2 S Ag 2 S + H 2 5 C. SiO 2 + 4HF SiF 4 + 2H 2 O 5 D. PbCl 2 + K 2 SO 4 2KCl + PbSO 4 2 E. K 2 CO 3 K 2 O + CO 2 3 F. C 2 H 4 + 3O 2 2CO 2 + 2H 2 O