Development Concept Of Reduction-Oxidation Reaction

Development Concept of Reduction-Oxidation Reaction The understanding of the concept of oxidation-reduction reaction has undergone three stages of development as follows. 1. Based on the Binding and Release of Oxygen a. Reduction is the reaction of releasing oxygen from a compound. Reducing agents are: 1) Substances that attract oxygen in reduction reactions. 2) Substances that undergo oxidation reactions. Example: 1) Reduction of Fe2 O3 by CO Fe2 O3 + 3 CO 2 Fe + 3 CO2 2) Reduction of Cr2 O3 by Al Cr2 O3 + 2 Al 2 Cr + Al2 O3 b. Oxidation is the reaction of binding (aggregating) oxygen by a substance. Oxidizing agents are: 1) Source of oxygen in oxidation reactions. 2) Substances that experience reduction. Example: 1) Oxidation of Fe by O2 4 Fe + 3 O2 2 Fe2 O3 2) ZnS roasting 2 ZnS + 3 O2 2 ZnO + 2 SO2 2. Based on Electron Binding and Releasing a. Reduction is an electron gain reaction. Reducers are: 1) A substance that loses electrons. 2) Substances that undergo oxidation. Example: 1) Cl2 + 2 e– 2 Cl– 2) Ca2+ + 2e– Ca b. Oxidation is a reaction with the loss of electrons. Oxidizing agents are: 1) Substances that bind electrons. 2) Substances that experience reduction. Example: 1) K K+ + e– 2) Cu Cu2+ + 2 e– 3. Based on the increase and decrease in oxidation number a. Reduction is the reaction of decreasing the oxidation number. A reducing agent is: 1) A substance that reduces another substance in a redox reaction. 2) Substances that undergo oxidation. Example: 2 SO3 2 SO2 + O2 The oxidation number of S in SO3 is +6 while in SO2 it is +4. Because element S has decreased its oxidation number, from +6 to +4, SO3 undergoes a reduction reaction. The oxidizing agent is SO3 and the reducing agent is SO2 . b. Oxidation is an increase in oxidation number reaction. Oxidizing agents are: 1) Substances that oxidize other substances in redox reactions. 2) Substances that undergo reduction reactions. Example: 4 FeO + O2 2 Fe2 O3 The oxidation number of Fe in FeO is +2, whereas in Fe2 O3 it is +3. Because the element Fe experienced an increase in its oxidation number, from +2 to +3, FeOunderwent an oxidation reaction. The reducing agent is FeO and the product of the oxidation is Fe2O3. If a chemical reaction undergoes both reduction and oxidation reactions in one reaction, the reaction is called a reduction-oxidation reaction or a redox reaction. Example: a. 4 FeO + O2 2 Fe2 O3 Fe2 O3 + 3 CO b. 2 Fe2 O3 2 Fe + 3 CO2 (not a redox reaction) (redox reaction) Exercise 1 1. Explain the meaning of redox reactions according to the three developmental concepts! 2. When is a reaction said to experience reduction and when to undergo oxidation? Give an example of each reaction!