TYPES OF CHEMICAL REACTIONS Precipitation Reactions Acids Bases Neutralization Combustion Oxidation-Reduction 1

2 Oxidation-Reduction Reactions (electron transfer reactions) 2Mg 2Mg e - O 2 + 4e - 2O 2- Oxidation half-reaction (lose e - ) Reduction half-reaction (gain e - ) 2Mg + O 2 + 4e - 2Mg O e - 2Mg + O 2 2MgO

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Types of Chemical Reactions Oxidation Reduction Reactions Electrons are transferred Oxidation: Loss of Electrons Reduction: Acceptance of Electrons

5 Zn (s) + CuSO 4 (aq)  ZnSO 4 (aq) + Cu (s) Cu (s) + 2AgNO 3 (aq)  Cu(NO 3 ) 2 (aq) + 2Ag (s)

Types of Re Dox Reactions Single Displacement With Metals Zn + HCl  ZnCl 2 + H 2 A + BC  AC + B Li + HOH  Ca + HNO 3  6

7 Displacement Reaction A + BC AC + B Sr + 2H 2 O Sr(OH) 2 + H 2 TiCl 4 + 2Mg Ti + 2MgCl 2 Cl 2 + 2KBr 2KCl + Br 2 Hydrogen Displacement Metal Displacement Halogen Displacement Types of Oxidation-Reduction Reactions

8 Types of Oxidation-Reduction Reactions Combination Reaction A + B C 2Al + 3Br 2 2AlBr 3 Decomposition Reaction 2KClO 3 2KCl + 3O 2 C A + B

9 Types of Oxidation-Reduction Reactions Combustion Reaction A + O 2 B S + O 2 SO Mg + O 2 2MgO

10 The Activity Series for Metals M + BC MC + B Hydrogen Displacement Reaction M is metal BC is acid or H 2 O B is H 2 Ca + 2H 2 O Ca(OH) 2 + H 2 Pb + 2H 2 O Pb(OH) 2 + H 2

Problem 4.54 PREDICT THE OUTCOME (COMPLETE THE PRODUCT SIDE) FOR THE FOLLOWING REACTIONS AND BALANCE THE EQUATIONS (a) Cu (s) + HCl (aq)  (b) I 2 (s) + NaBr (aq)  (c ) Mg (s) + CuSO 4 (aq)  (d) Cl 2 (g) + KBr 4 (aq) 

12 Oxidation number The charge the atom would have in a molecule (or an ionic compound) if electrons were completely transferred. 1.Free elements (uncombined state) have an oxidation number of zero. Na, Be, K, Pb, H 2, O 2, P 4 = 0 2.In monatomic ions, the oxidation number is equal to the charge on the ion. Li +, Li = +1; Fe 3+, Fe = +3; O 2-, O = -2 3.The oxidation number of oxygen is usually –2. In H 2 O 2 and O 2 2- it is –1. 4.4

13 4.The oxidation number of hydrogen is +1 except when it is bonded to metals in binary compounds. In these cases, its oxidation number is –1. 6. The sum of the oxidation numbers of all the atoms in a molecule or ion is equal to the charge on the molecule or ion. 5.Group IA metals are +1, IIA metals are +2 and fluorine is always –1. HCO 3 - O = – 2H = +1 3x( – 2) ? = – 1 C = +4 What are the oxidation numbers of all the elements in HCO 3 - ? 7. Oxidation numbers do not have to be integers. Oxidation number of oxygen in the superoxide ion, O 2 -, is –½.

14 The Oxidation Numbers of Elements in their Compounds