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1、,*,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Balancing Oxidation-Reduction Reactions,Any reaction involving the transfer of electrons is an oxidation-reduction(or redox)reaction,Balancing Oxidation-Reduction,1,Definitions:,Oxi

2、dation is,the loss of electrons,.,Reduction is,the gain of electrons.,Oxidation cannot take place without reduction.,During a redox reaction,the oxidation numbers of reactants will change.,Definitions:Oxidation is the l,2,For any equation to be balanced:,1.The number of atoms of each type on the lef

3、t side of the arrow must equal the number of atoms of each type to the right of the arrow.,2.The total charges of all the ions on the left side of the arrow must equal the total charges of all the ions to the right of the arrow.,For any equation to be balance,3,In addition,for redox reactions:,3.The

4、 electrons lost(during oxidation)must equal the electrons gained(during reduction).,In addition,for redox reactio,4,Balancing Oxidation-Reduction Reactions:,1.Assign oxidation numbers to every atom in the reaction.,Cr,2,O,7,2-,+C,2,O,4,2-,Cr,3+,+CO,2,Balancing Oxidation-Reduction,5,Balancing Oxidati

5、on-Reduction Reactions:,1.Assign oxidation numbers to every atom in the reaction.,Cr,2,O,7,2-,+C,2,O,4,2-,Cr,3+,+CO,2,Oxygen,in a compound or ion,is-2,Balancing Oxidation-Reduction,6,Balancing Oxidation-Reduction Reactions:,1.Assign oxidation numbers to every atom in the reaction.,Cr,2,O,7,2-,+C,2,O

6、,4,2-,Cr,3+,+CO,2,Use the combined charges of the oxygens in each ion or compound to determine the oxidation number of Cr or C.,Balancing Oxidation-Reduction,7,Balancing Oxidation-Reduction Reactions:,1.Assign oxidation numbers to every atom in the reaction.,Cr,2,O,7,2-,+C,2,O,4,2-,Cr,3+,+CO,2,-14-8

7、-4,Use the combined charges of the oxygens in each ion or compound to determine the oxidation number of Cr or C.,Balancing Oxidation-Reduction,8,Balancing Oxidation-Reduction Reactions:,1.Assign oxidation numbers to every atom in the reaction.,Cr,2,O,7,2-,+C,2,O,4,2-,Cr,3+,+CO,2,-14-8-4,The sum of t

8、he oxidation numbers of the other element must add up to the charge on the ion or molecule.,Balancing Oxidation-Reduction,9,Balancing Oxidation-Reduction Reactions:,1.Assign oxidation numbers to every atom in the reaction.,Cr,2,O,7,2-,+C,2,O,4,2-,Cr,3+,+CO,2,+12-14 +6-8 +3 +4-4,The sum of the oxidat

9、ion numbers of the other element must add up to the charge on the ion or molecule.,Balancing Oxidation-Reduction,10,Balancing Oxidation-Reduction Reactions:,1.Assign oxidation numbers to every atom in the reaction.,Cr,2,O,7,2-,+C,2,O,4,2-,Cr,3+,+CO,2,+12 +6 +3 +4,Divide the sum of the charges by the

10、 number of atoms to get the oxidation number for chromium and carbon in the reactants.,Balancing Oxidation-Reduction,11,Balancing Oxidation-Reduction Reactions:,1.Assign oxidation numbers to every atom in the reaction.,Cr,2,O,7,2-,+C,2,O,4,2-,Cr,3+,+CO,2,+12/2=+6 +6/2=+3 +3 +4,Divide the sum of the

11、charges by the number of atoms to get the oxidation number for chromium and carbon in the reactants.,Balancing Oxidation-Reduction,12,Balancing Oxidation-Reduction Reactions:,2.Write bare bones half reactions.,Include only the atom,ion or element that changes oxidation number.,Cr,+6,+3e,-,Cr,+3,C,+3

12、,C,+4,+1e,-,Remember that each half reaction must also be balanced for charge.The total charges on the left must equal the total charges on the right.,Balancing Oxidation-Reductio,13,Balancing Oxidation-Reduction Reactions:,3.Take into account any subscripts in the formulas of reactants and products

13、,and multiply the half reactions accordingly.,Cr,2,O,7,2-,+C,2,O,4,2-,Cr,3+,+CO,2,2Cr,+6,+3e,-,Cr,+3,2C,+3,C,+4,+1e,-,Balancing Oxidation-Reductio,14,Balancing Oxidation-Reduction Reactions:,3.Take into account any subscripts in the formulas of reactants and products,and multiply the half reactions

14、accordingly.,Cr,2,O,7,2-,+C,2,O,4,2-,Cr,3+,+CO,2,2Cr,+6,+6e,-,2 Cr,+3,2C,+3,2 C,+4,+2e,-,Balancing Oxidation-Reductio,15,Balancing Oxidation-Reduction Reactions:,4.Multiply each half reaction by the appropriate factor so that the number of electrons lost=number of electrons gained.,12Cr,+6,+6e,-,2 C

15、r,+3,32C,+3,2 C,+4,+2e,-,Balancing Oxidation-Reductio,16,Balancing Oxidation-Reduction Reactions:,4.Multiply each half reaction by the appropriate factor so that the number of electrons lost=number of electrons gained.,2Cr,+6,+6e,-,2 Cr,+3,6C,+3,6 C,+4,+6e,-,Balancing Oxidation-Reductio,17,Balancing

16、 Oxidation-Reduction Reactions:,4.Add the two half reactions together.,2Cr,+6,+6e,-,2 Cr,+3,6C,+3,6 C,+4,+6e,-,2Cr,+6,+6C,+3,2 Cr,+3,+6 C,+4,Balancing Oxidation-Reductio,18,Balancing Oxidation-Reduction Reactions:,4.Add the two half reactions together.,2Cr,+6,+6e,-,2 Cr,+3,6C,+3,6 C,+4,+6e,-,2Cr,+6,+6C,+3,2 Cr,+3,+6 C,+4,At this point,the electrons lost=the electrons gained during the reaction.,Balancing Oxidation-Reductio,19,Balancing Oxidation-Reduction Reactions:,5.You now have the number of