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

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

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

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

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

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

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

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.

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

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

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.

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings NH 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

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

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

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 15  To balance an equation, place coefficients in front of the appropriate formulas. 4 NH 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

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

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 17 Check the balance of atoms in the following: Fe 3 O 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

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 18 Fe 3 O 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

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 –

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

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

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

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 23 A. 2) 2, 3, 4, 3 2 Fe 2 O 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 ) H 2 Solution

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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