2. 1 Chemical Reactions

3. 2 l All chemical reactions have two parts: 1)A substance that undergoes a reaction is called a reactant. In other words, reactants are the substances you start with.

4. 3 Chemical Reactions 2)When reactants undergo a chemical change, each new substance formed is called a product. In other words, the products are the substances you end up with.

5. 4 Chemical Reactions l The reactants turn into the products. Reactants  Products

6. 5 Chemical Reactions l In a chemical reaction, the way atoms are joined is changed. l Atoms aren’t created or destroyed.

7. 6 Chemical Reactions l Chemical reactions can be described several ways.  In a sentence Copper reacts with chlorine to form copper (II) chloride.  In a word equation Copper + chlorine  copper (II) chloride

8. 7 Symbols Used in Equations l The arrow separates the reactants from the products l The arrow reads “reacts to form.” l The plus sign reads “and”

9. 8 Symbols Used in Equations l (s) after the formula - solid l (g) after the formula - gas ( l ) after the formula – liquid l (aq) after the formula – aqueous (a solid dissolved in water)

10. 9 Symbols Used in Equations  used after a product indicates a gas, same as (g)  used after a product indicates a solid, same as (s)

11. 10 Symbols Used in Equations l indicates a reversible reaction. (More info later) l shows that heat is supplied to the reaction l is used to indicate a catalyst used supplied, in this case, platinum.

12. 11 What is a Catalyst? l A catalyst is a substance that speeds up a reaction without being changed by the reaction. l Enzymes are biological or protein catalysts.

13. 12 Diatomic Elements l There are 8 elements that never want to be alone. l They form diatomic molecules. H 2, N 2, O 2, F 2, Cl 2, Br 2 and I 2 l The –ogens and the –ines l 1 + 7 pattern on the periodic table

14. 13 Diatomic Elements

15. 14 Indications of a Chemical Reaction l The following are indications that a chemical reaction has occurred:  formation of a precipitate  evolution of a gas  color change  absorption or release of heat

16. 15 Skeleton Equation l A skeleton formula uses formulas and symbols to describe a reaction. l All chemical equations are sentences that describe reactions.

17. 16 Problem l Convert the following sentence to a chemical equation.  Solid iron (III) sulfide reacts with gaseous hydrogen chloride to form solid iron (II) chloride and hydrogen sulfide gas. Fe 2 S 3 (s) + HCl (g)  FeCl 2 (s) + H 2 S (g)

18. 17 Problem l Convert the following sentence to a chemical equation.  Nitric acid dissolved in water reacts with solid sodium carbonate to form liquid water and carbon dioxide gas and sodium nitrate dissolved in water. HNO 3 (aq) + Na 2 CO 3 (s)  H 2 O ( l ) + CO 2 (g) + NaNO 3 (aq)

19. 18 Problem l Convert the following chemical equation to a sentence.  Fe (s) + O 2 (g)  Fe 2 O 3 (s) Solid iron reacts with oxygen gas to form solid iron (III) oxide.

20. 19 Problem l Convert the following chemical equation to a sentence.  Cu (s) + AgNO 3 (aq)  Ag (s) + Cu(NO 3 ) 2 (aq) Solid copper reacts with silver nitrate dissolved in water to form solid silver and copper (II) nitrate dissolved in water.

21. 20 Balancing Chemical Equations

22. 21 The Balanced Equation l Atoms can’t be created or destroyed. l All the atoms we start with we must end up with. l A balanced equation has the same number of each element on both sides of the equation.

23. 22 C + O 2  CO l This equation is NOT balanced. l There is one carbon atom on the left and one on the right. l There are two oxygen atoms on the left and only one on the right. C + O  C O O

24. 23 C + O 2  CO l We need one more oxygen atom in the products. l We can’t change the formula, because it describes what it is. C + O  C O O

25. 24 l In order to have two oxygen atoms, another CO must be produced. l But where did the other carbon come from? C + O  C O O O C

26. 25 l We must have started with two carbon atoms. C + O  C O O O C C

27. 26 l The balanced chemical equation is 2 C + O 2  2 CO C + O  C O O O C C

28. 27 Rules for Balancing 1. Write the correct formulas for all the reactants and products. 2. Count the number of atoms of each type appearing on both sides. 3. Balance the elements one at a time by adding coefficients (the numbers in front). 4. Check to make sure it is balanced.

29. 28 Never l Never change a subscript to balance an equation. l If you change the formula you are describing a different reaction.

30. 29 Never l Never put a coefficient in the middle of a formula. l 2 NaCl is okay; Na2Cl is not.

31. 30 Example H 2 +H2OH2O O2O2  Make a table to keep track of where you are in the balancing process.

32. 31 Example H 2 +H2OH2O O2O2  We need twice as much O in the product. ReactantsProducts H O 2 2 2 1

33. 32 Example H 2 +H2OH2OO2O2  We need 2 oxygen atoms on the product side, so a coefficient of 2 should be placed in front of water. 2

34. 33 Example H 2 +H2OH2OO2O2  We must recalculate the number of hydrogen and oxygen atoms on the right. Coefficients are used as multipliers. RP H O 2 2 2 1 2 4 2

35. 34 Example H 2 +H2OH2OO2O2  Now we need 4 hydrogen atoms on the reactant side. RP H O 2 2 4 2 2

36. 35 Example H 2 +H2OH2OO2O2  A coefficient of 2 should be placed in front of hydrogen gas. RP H O 2 2 4 2 22 4

37. 36 Example H 2 +H2OH2OO2O2  The equation is balanced; it has the same number of each kind of atom on both sides! RP H O 4 2 4 2 22

38. 37 Example H 2 +H2OH2OO2O2  This is the answer, RP H O 2 2 2 1 2 2 4 2 4 not this.

39. 38 Balancing Hints l Balance elements in the following order:  metals  nonmetals  hydrogen  oxygen

40. 39 Balancing Hints l If an atom appears more than once on a side, balance it last. l If you fix everything except one element, and it is even on one side and odd on the other, double the first number, then move on from there.

41. 40 Problem l Balance the following equation.  CH 4 + O 2  CO 2 + H 2 O CH 4 + 2 O 2  CO 2 + 2 H 2 O

42. 41 Problem 2 AgNO 3 + Cu  Cu(NO 3 ) 2 + 2 Ag l Balance the following equation.  AgNO 3 + Cu  Cu(NO 3 ) 2 + Ag

43. 42 Problem l Balance the following equation.  Mg + N 2  Mg 3 N 2 3 Mg + N 2  Mg 3 N 2

44. 43 Problem l Balance the following equation.  P + O 2  P 4 O 10 4 P + 5 O 2  P 4 O 10

45. 44 Problem l Balance the following equation.  Na + H 2 O  H 2 + NaOH 2 Na + 2 H 2 O  H 2 + 2 NaOH

46. 45 Problem l Balance the following equation.  Pb(NO 3 ) 2 + K 2 CrO 4  PbCrO 4 + KNO 3 Pb(NO 3 ) 2 + K 2 CrO 4  PbCrO 4 + 2 KNO 3

47. 46 Problem l Balance the following equation.  MnO 2 + HCl  MnCl 2 + H 2 O+ Cl 2 MnO 2 + 4 HCl  MnCl 2 + 2 H 2 O+ Cl 2

48. 47 Problem l Balance the following equation.  Ba(CN) 2 + H 2 SO 4  BaSO 4 + HCN Ba(CN) 2 + H 2 SO 4  BaSO 4 + 2 HCN

49. 48 Problem l Balance the following equation.  Zn(OH) 2 + H 3 PO 4  Zn 3 (PO 4 ) 2 + H 2 O  3 Zn(OH) 2 + 2 H 3 PO 4  Zn 3 (PO 4 ) 2 + 6 H 2 O

50. 49 Types of Reactions Predicting the Products

51. 50 Types of Reactions

52. 51 Types of Reactions l Reactions fall into 5 categories. l We will recognize the type by the reactants. l We will be able to predict the products. l For some we will be able to predict whether they will happen at all.

53. 52 Synthesis Reactions l Synthesize - put together l Whenever two or more substances combine to form one single product, the reaction is called a synthesis reaction. Ca + O 2  CaO P 2 O 5 + 3 H 2 O  2 H 3 PO 4

54. 53 Synthesis Reactions

55. 54 Synthesis Reactions l We can predict the products if they are two elements. l All you need to do is combine the elements, metals first, and criss- cross oxidation numbers if necessary.

56. 55 Synthesis Reactions l Example  Mg + N 2  MgN 2+ 3-

57. 56 Synthesis Reactions l The charges do not add to give zero. MgN 2+3- 23

58. 57 Synthesis Reactions l Example  Mg + N 2  Mg 3 N 2

59. 58 Synthesis Reactions l Now the reaction needs to be balanced.  Mg + N 2  Mg 3 N 2 3

60. 59 Synthesis Reactions l Example  CaO + H 2 O  l On page 6 of the Chemistry Reference Packet, this reaction is an example of “Metal oxide - water reactions.”

61. 60 Synthesis Reactions l Example  CaO + H 2 O  l The product listed in the packet is “base.” A base is a metallic hydroxide.

62. 61 Synthesis Reactions l Example  CaO + H 2 O  CaOH 2+ 1-

63. 62 Synthesis Reactions l The charges do not add to give zero, so you must criss-cross. l The hydroxide needs parenthesis. CaOH 2+1- 21 ()

64. 63 Synthesis Reactions l Example  CaO + H 2 O  Ca(OH) 2

65. 64 Synthesis Reactions l Check the balancing.  CaO + H 2 O  Ca(OH) 2 l The reaction is already balanced!

66. 65 Synthesis Reactions l Example  SO 2 + H 2 O  l On page 6 of the Chemistry Reference Packet, this reaction is an example of “Nonmetal oxide - water reactions.”

67. 66 Synthesis Reactions l Example  SO 2 + H 2 O  l The product listed in the packet is “acid.” The acid is a ternary acid. l Ternary acids start with H and end in O.

68. 67 Synthesis Reactions l Example  SO 2 + H 2 O  l The other element goes in the center.

69. 68 Synthesis Reactions l Example  SO 2 + H 2 O  HOS l This is the only compound for which you can add the number of elements and use these numbers as subscripts.

70. 69 Synthesis Reactions l Example  SO 2 + H 2 O  HOS l There are 2 hydrogens. 2 l There is one sulfur. l There are three oxygens. 13

71. 70 Synthesis Reactions l Example  SO 2 + H 2 O  H 2 SO 3 l The reaction is balanced.

72. 71 Synthesis Reactions l Example  CaO + H 2 O  Ca(OH) 2

73. 72 Synthesis Reactions l Check the balancing.  CaO + H 2 O  Ca(OH) 2 l The reaction is already balanced!

74. 73 Problem l Write and balance the following synthesis reaction.  Ca + Cl 2  l Remember that the first step is to write the formula. l Then balance. Ca + Cl 2  CaCl 2

75. 74 Problem l Write and balance the following synthesis reaction.  Fe + O 2  HINT: Use iron (II). 2 Fe + O 2  2 FeO

76. 75 Problem l Write and balance the following synthesis reaction.  K 2 O + H 2 O  K 2 O + H 2 O  2 KOH

77. 76 Problem l Write and balance the following synthesis reaction.  Al + O 2  4 Al + 3 O 2  2 Al 2 O 3

78. 77 Problem l Write and balance the following synthesis reaction.  SO 3 + H 2 O  SO 3 + H 2 O  H 2 SO 4

79. 78 Problem l Write and balance the following synthesis reaction.  N 2 O 5 + H 2 O  N 2 O 5 + H 2 O  2 HNO 3

80. 79 Decomposition Reactions l decompose = fall apart l In a decomposition reaction, one compound breaks down into two or more simpler substances. l NaCl Na + Cl 2 l CaCO 3 CaO + CO 2

81. 80 Decomposition Reactions

82. 81 Decomposition Reactions l Can predict the products if it is a binary compound. l A binary compound is made up of only two elements. l The compound merely falls apart into its elements.

83. 82 Decomposition Reactions lH2OlH2O H + O Both of these elements are diatomic!!! 22

84. 83 Decomposition Reactions lH2OlH2O H + O Now we must balance. 22 H 2 O H 2 + O 2 22

85. 84 Decomposition Reactions Hg + O Oxygen is diatomic!!! 2 l HgO

86. 85 Decomposition Reactions l HgO Hg + O Now we must balance. 2 HgO Hg + O 2 22

87. 86 Decomposition Reactions l If the compound has more than two elements, you must consult the Reference Tables, page 6.

88. 87 Example l Write and balance the following decomposition reaction.  NiCO 3 l Once again, refer to page 6 in the Chemistry Reference Packet.

89. 88 Example  NiCO 3 l NiCO 3 is called nickel (II) carbonate. l The packet states that a metallic carbonate decomposes to form a MO (metallic oxide) and CO 2.

90. 89 Example  NiCO 3 l The metallic oxide is nickel (II) oxide. Ni 2+ O 2- l The two oxidation numbers add to give zero, so the formula is NiO.

91. 90 Example  NiCO 3 l Check the balancing. l The reaction is already balanced! NiO + CO 2

92. 91 Problem l Write and balance the following decomposition reaction.  KClO 3  2 KClO 3  2 KCl + 3 O 2

93. 92 Problem l Write and balance the following decomposition reaction.  CaBr 2  CaBr 2  Ca + Br 2

94. 93 Problem l Write and balance the following decomposition reaction.  Li 2 CO 3  Li 2 CO 3  Ca + Br 2

95. 94 Problem l Write and balance the following decomposition reaction.  Cr(OH) 2  Cr(OH) 2  CrO + H 2 O

96. 95 Problem l Write and balance the following decomposition reaction.  NaHCO 3  2 NaHCO 3  Na 2 O + H 2 O + 2 CO 2

97. 96 Problem l Write and balance the following decomposition reaction.  HNO 3  2 HNO 3  N 2 O 5 + H 2 O l Dinitrogen pentoxide one of the products.

98. 97 Single Replacement l In a single-displacement reaction, one element takes the place of another in a compound. l One reactant must be an element and one reactant must be a compound. l The products will be a different element and a different compound. F 2 + LiCl  LiF + Cl 2

99. 98 Single Replacement l Remember zinc, Zn, always forms a +2 ion doesn’t need parenthesis. l ZnCl 2 is zinc chloride. l In addition, silver, Ag, always forms a +1 ion. l AgCl is silver chloride.

100. 99 Single Replacement l Some single replacement reactions do not occur because some elements are not as active as others.

101. 100 Single Replacement l There is a list referred to as the Activity Series on page 7 of your Chemistry Reference Packet. l A higher element on the list replaces lower element. l If the element by itself is lower on the list, the reaction will NOT occur.

102. 101 Single Replacement l Metals replace metals  K + NaCl  l Potassium wants to replace sodium. l You must check the activity series on page 7 of your Chemistry Reference Packet to see if this is possible.

103. 102 Single Replacement l Metals replace metals  K + NaCl  l Is potassium higher than sodium on the Activity Series of Metals? YES!!

104. 103 Single Replacement l Metals replace metals  K + NaCl  l Because K is higher, potassium can replace sodium. l The potassium will bond with the chlorine and the sodium will be alone. KCl + Na

105. 104 Single Replacement l Metals replace metals  K + NaCl  KCl + Na l You must always check to see if the compound formed needs criss- crossing. KCl 1+1-

106. 105 Single Replacement l Metals replace metals  K + NaCl  KCl + Na l Since the charges add to get zero, the formula remains KCl.

107. 106 Single Replacement l Metals replace metals  K + NaCl  KCl + Na l Check for balancing. l The reaction is balanced!

108. 107 Single Replacement l Metals replace metals  Sn + FeCl 3  l Tin wants to replace iron. l You must check the activity series on page 7 of your Chemistry Reference Packet to see if this is possible.

109. 108 Single Replacement l Metals replace metals  Sn + FeCl 3  l Is tin higher than iron on the Activity Series of Metals? NO!!

110. 109 Single Replacement l Metals replace metals  Sn + FeCl 3  l Because Sn is NOT higher, tin cannot replace iron. l No reaction occurs. No reaction

111. 110 Problem l Write and balance the following single replacement reaction.  Rb + AlN  3 Rb + AlN  Rb 3 N + Al

112. 111 Problem l Write and balance the following single replacement reaction.  Zn + HCl  Zn + 2 HCl  ZnCl 2 + H 2

113. 112 Problem l Write and balance the following single replacement reaction.  Ag + CoBr 2  Ag + CoBr 2  no reaction

114. 113 Single Replacement l Metals replace hydrogen  Na + H 2 O (cold)  l Think of water as HOH. l Metals high enough on the activity series replace the first H and combine with the OH 1- (hydroxide) according to page 6 of the Reference Tables.

115. 114 Single Replacement Na + HOH (cold)  l Is sodium above hydrogen and higher than the line marked “Replace hydrogen from cold water” on the activity series? YES!!

116. 115 Single Replacement Na + HOH (cold)  l Sodium replaces the first H, bonding with hydroxide. NaOH + H

117. 116 Single Replacement Na + H 2 O (cold)  l But hydrogen is diatomic. NaOH + H 2 l Now check the criss-crossing for NaOH.

118. 117 Single Replacement Na + H 2 O (cold)  NaOH + H 2 Na 1- OH 1+ l No criss-crossing is needed for NaOH.

119. 118 Single Replacement Na + H 2 O (cold)  NaOH + H 2 l Now check the balancing. l The 2’s are needed to balance the hydrogens, but now Na is not balanced. 22

120. 119 Single Replacement Na + 2H 2 O (cold)  2NaOH + H 2 l Now the reaction is balanced! 2

121. 120 Single Replacement l Metals replace hydrogen  Mg + HCl  l Metals higher on the activity series replace the H and combine with the nonmetal according to page 6 of the Reference Tables. Hydrogen gas is a second product.

122. 121 Single Replacement Mg + HCl  l Is magnesium above hydrogen on the activity series? YES!!

123. 122 Single Replacement Mg + HCl  l Magnesium replaces the H, bonding with the chloride ion. MgCl + H

124. 123 Single Replacement Mg + HCl  l But hydrogen is diatomic. MgCl + H 2 l Now check the criss-crossing for MgCl.

125. 124 Single Replacement Mg + HCl  MgCl + H 2 Mg 1- Cl 2+ l Criss-crossing is needed. MgCl 2

126. 125 Single Replacement Mg + HCl  MgCl 2 + H 2 l Now check the balancing. l The 2 is added to balance the hydrogen and the chlorine. 2

127. 126 Problem l Write and balance the following single replacement reaction.  Ag + H 2 O (steam)  Ag + H 2 O (steam)  no reaction

128. 127 Problem l Write and balance the following single replacement reaction.  Cu + H 2 SO 4  Cu + H 2 SO 4  no reaction

129. 128 Problem l Write and balance the following single replacement reaction.  Cr + H 3 PO 4   (HINT: Use Cr 3+ ) 2Cr + 2H 3 PO 4  2CrPO 4 + 3H 2

130. 129 Problem l Write and balance the following single replacement reaction.  Ca + H 2 O (steam)  Ca + 2H 2 O (steam)  Ca(OH) 2 + H 2

131. 130 Single Replacement l Nonmetals can replace other nonmetals. This is limited to F 2, Cl 2, Br 2, I 2 l The order of activity is listed in the Chemistry Reference Packet, page 7. l Higher replaces lower.

132. 131 Single Replacement F 2 + HCl  l Is fluorine above chlorine in the activity series of halogens? YES!!

133. 132 Single Replacement F 2 + HCl  l Fluorine replaces the chlorine, bonding with hydrogen. HF + Cl

134. 133 Single Replacement F 2 + HCl  l But chlorine is diatomic. HF + Cl 2 l Check the oxidation numbers of H and F. H 1+ F 1-

135. 134 Single Replacement F 2 + HCl  l Check balancing. HF + Cl 2 F 2 + HCl  HF + Cl 2 22

136. 135 Problem l Write and balance the following single replacement reaction.  Br 2 + KCl  Br 2 + KCl  no reaction

137. 136 Problem l Write and balance the following single replacement reaction.  Cl 2 + K I  Cl 2 + 2 K I  2 KCl + I 2

138. 137 Double Replacement l In double-displacement reactions, the positive portions of two ionic compounds are interchanged. l The reactants must be two ionic compounds or acids. l Double replacement reactions usually take place in aqueous solution.

139. 138 Double Replacement NaOH + FeCl 3  l The positive ions change place. l You must check to see if you need to criss-cross the products. NaOH + FeCl 3  Fe(OH) 3 + NaCl NaOH + FeCl 3  Fe +3 OH - + Na +1 Cl -1

140. 139 Double Replacement NaOH + FeCl 3  Fe(OH) 3 + NaCl l Now balance. NaOH + FeCl 3  Fe(OH) 3 + NaCl 33

141. 140 Double Replacement l A double replacement reaction will only happen if one of the products:  doesn’t dissolve in water and forms a solid,  is a gas that bubbles out, or  is a covalent compound usually water.

142. 141 Double Replacement 3NaOH + FeCl 3  Fe(OH) 3 + 3NaCl l None of the products are familiar gases. Both products are ionic (not covalent) because they start with metals.

143. 142 Double Replacement 3NaOH + FeCl 3  Fe(OH) 3 + 3NaCl l We must consult the Solubility Rules on page 6 of the Chemistry Reference Tables to determine if a solid (a precipitate) is formed.

144. 143 Double Replacement 3NaOH + FeCl 3  Fe(OH) 3 + 3NaCl The “Soluble” side of the Solubility Rules states that Group 1 ( I A) salts are soluble; therefore, NaCl is soluble and is NOT the precipitate.

145. 144 Double Replacement 3NaOH + FeCl 3  Fe(OH) 3 + 3NaCl l The “Insoluble” side of the Solubility Rules states that all hydroxides except Group 1, Sr 2+, Ba 2+ and NH 4 1+ are INSOLUBLE. l Therefore, Fe(OH) 3 is the precipitate (solid).

146. 145 Net Ionic Equations l In molecular equations, the formulas of the compounds are written as though all species existed as molecules or whole units.

147. 146 l An ionic equation shows dissolved ionic compounds in terms of their free ions. Net Ionic Equations

148. 147 l Ions that are not involved in the overall reaction are called spectator ions. The net ionic equation indicates only the species that actually take part in the reaction. Net Ionic Equations

149. 148 The following steps are useful for writing ionic and net ionic equations: 1) Write a balanced molecular equation for the reaction. Net Ionic Equations

150. 149 2)Rewrite the equation to indicate which substances are in ionic form in solution. Remember that all soluble salts (and other strong electrolytes), are completely dissociated into cations and anions. This procedure gives us the ionic equation. Net Ionic Equations

151. 150 3)Lastly, identify and cancel spectator ions on both sides of the equation to arrive at the net ionic equation. Net Ionic Equations

152. 151 Molecular equation: Complete ionic equation: 3Na + + 3OH - + Fe 3+ + 3Cl -  Fe(OH) 3 + 3Na + + 3Cl - Net ionic equation: 3OH - (aq) + Fe 3+ (aq)  Fe(OH) 3 (s) 3NaOH + FeCl 3  Fe(OH) 3 + 3NaCl

153. 152 Problem l Write and balance the following double replacement reaction. Assume the reaction takes place.  CaCl 2 + NaOH  CaCl 2 + 2 NaOH  Ca(OH) 2 + 2 NaCl

154. 153 Problem l Identify the precipitate and write the net ionic equation. CaCl 2 + 2 NaOH  Ca(OH) 2 + 2 NaCl Ca(OH) 2 is the precipitate. Ca 2+ + 2OH -  Ca(OH) 2

155. 154 Problem l Write and balance the following double replacement reaction. Assume the reaction takes place.  CuCl 2 + K 2 S  CuCl 2 + K 2 S  CuS + 2 KCl

156. 155 Problem l Identify the precipitate and write the net ionic equation. CuCl 2 + K 2 S  CuS + 2 KCl CuS is the precipitate. Cu 2+ + S 2-  CuS

157. 156 Problem l Write and balance the following double replacement reaction. Assume the reaction takes place.  KOH + Fe(NO 3 ) 3  3 KOH + Fe(NO 3 ) 3  3 KNO 3 + Fe(OH) 3

158. 157 Problem l Identify the precipitate and write the net ionic equation. 3 KOH + Fe(NO 3 ) 3  3 KNO 3 + Fe(OH) 3 Fe(OH) 3 is the precipitate. Fe 3+ + 3OH -  Fe(OH) 3

159. 158 Problem l Write and balance the following double replacement reaction. Assume the reaction takes place.  (NH 4 ) 2 SO 4 + BaF 2  (NH 4 ) 2 SO 4 + BaF 2  2 NH 4 F + BaSO 4

160. 159 Problem l Identify the precipitate and write the net ionic equation. (NH 4 ) 2 SO 4 + BaF 2  2 NH 4 F + BaSO 4 BaSO 4 is the precipitate. Ba 2+ + SO 4 2-  BaSO 4

161. 160 Combustion l A combustion reaction is one in which a substance rapidly combines with oxygen to form one or more oxides. l Combustion reactions involve a compound composed of only C and H (and maybe O) that is reacted with oxygen gas.

162. 161 Combustion l If the combustion is complete, the products will be CO 2 and H 2 O. l Combustion reactions produce heat, and are therefore considered exothermic reactions.

163. 162 Combustion

164. 163 Combustion

165. 164 Combustion l Complete and balance the following combustion reaction. CO 2 + H 2 O  C 4 H 10 + O 2  l Now balance.

166. 165 Combustion  C 4 H 10 + O 2  CO 2 + H 2 O 4513/2 l Fractions are not allowed, so multiply all coefficients by 2.  C 4 H 10 + O 2  CO 2 + H 2 O 281310

167. 166 Problem  C 6 H 12 O 6 + O 2  l Complete and balance the following combustion reaction. C 6 H 12 O 6 + 6 O 2  6 CO 2 + 6 H 2 O

168. 167 Problem  C 8 H 8 + O 2  l Complete and balance the following combustion reaction. C 8 H 8 + 10 O 2  8 CO 2 + 4 H 2 O

169. 168 Problem  C 3 H 8 O 3 + O 2  l Complete and balance the following combustion reaction. 2 C 3 H 8 O 3 + 7 O 2  6 CO 2 + 8 H 2 O

170. 169 How to Recognize Which Type l Look at the reactants. (E = element; C = compound) l E + E Synthesis l CDecomposition l E + CSingle replacement l C + CDouble replacement l CH cpd + O 2 Combustion

171. 170 How to Recognize Which Type l Note: Two other common synthesis reactions include: nonmetallic oxide + water and metallic oxide + water.

172. 171 Problem l Identify whether the reaction is synthesis, decomposition, single replacement, double replacement or combustion.  H 2 + O 2   H 2 O  (synthesis) (decomposition)

173. 172 Problem l Identify whether the reaction is synthesis, decomposition, single replacement, double replacement or combustion.  Mg(OH) 2 + H 2 SO 3   HgO  (double replacement) (decomposition)

174. 173 Problem l Identify whether the reaction is synthesis, decomposition, single replacement, double replacement or combustion.  KBr + Cl 2   Zn + H 2 SO 4  (single replacement)

175. 174 Problem l Identify whether the reaction is synthesis, decomposition, single replacement, double replacement or combustion.  AgNO 3 + NaCl   C 6 H 6 + O 2  (double replacement) (combustion)