Objectives Distinguish among the five major types of chemical reactions. Classify a reaction as belonging to one of five major types. Why Reactions Are Classified So that scientists could have an idea about what is going to happen when a particular reaction occurs. To know what type of products to expect and what precautions need to be taken. Major Classes of Reactions 1. Synthesis 2. Decomposition 3. Single-Displacement 4. Double-Displacement 5. Combustion Major Classes of Reactions Synthesis Synthesis- two or more substances combine to form one product. Examples 2 Na(s) + Cl 2 (g) 2 NaCl(s) 4 Fe(s) + 3 O 2 (g) 2Fe 2 O 3 (s) 2 CO(g) + O 2 (g) 2 CO 2 (g) Decomposition Decomposition a compound breaks down into two or more simpler substances. Examples 2 H 2 O(l) 2 H 2 (g) + O 2 (g) 2 HgO(l) 2 Hg(l) + O 2 (g) 2 H 2 O 2 (aq) 2 H 2 O(l) + O 2 (g) Single-Displacement Single-Displacement - one element takes the place of another in a compound Examples Fe(s) + CuSO 4 (aq) FeSO 4 (aq) + Cu(s) Cl 2 (g) + 2 NaBr(aq) 2 NaCl(aq) + Br 2 (l) Cl 2 (g) + 2 KBr(aq) 2 KCl(aq) + Br 2 (aq) Double-Displacement Double-Displacement positive portions of two ionic compounds are interchanged. One of the products is either a precipitate or water Examples Pb(NO 3 ) 2 (aq) + 2 KI(aq) PbI 2 (s) + 2 KNO 3 (aq) PbCl 2 (s) + Li 2 SO 4 (aq) PbSO 4 (s) +2 LiCl(aq) BaCl 2 (aq) + H 2 SO 4 (aq) 2 HCl(aq) + BaSO 4 (s) Combustion Combustion a substance rapidly combines with oxygen to form one or more oxides. Examples 2 C 2 H 2 (g) + 5 O 2 (g) 4 CO 2 (g) + 2 H 2 O(g) CH 4 (g) + 2 O 2 (g) CO 2 (g) + 2 H 2 O(g) C 6 H 12 O 6 (s) + 6 O 2 (g) 6 CO 2 (g) + 6 H 2 O(g) Table 6.1 Types of Reactions Reaction TypeGeneral Equation Synthesis Element/compound + element/compound compound Decomposition Compound two or more elements/compounds Single displacement Element a + compound bc element b + compound ac Double displacement Compound ac + compound bd compound ad + compound bc Combustion Element/compound + oxygen oxide (s) (many produce carbon dioxide and water) Review What are the five major types of reactions? Describe each and give an example. Homework Page 209 #1-3 Page 225 #6