electrochemistry_fall2011_preclass

electrochemistry_fall2011_preclass - Electrochemistry 4.5:

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Unformatted text preview: Electrochemistry 4.5: Oxidation-reduction (redox) reactions 21.1: Redox reactions and electrochemical cells 21.2: Voltaic cells: Using spontaneous reactions to generate electrical energy 21.3: Cell potential: Output of a voltaic cell 21.4: Free energy and electrical work 21.5: Electrochemical processes in batteries 21.6: Corrosion: A case of environmental chemistry 21.7: Electrolytic cells: Using electrical energy to drive nonspontaneous reactions 4.5: Oxidation-reduction (redox) reactions The key event in a redox reaction is the movement of electrons between reactants. Fig. 4.14 Redox: the movement of electrons between reactants. Fig. 4.1 a The key event in a redox reaction is the movement of electrons between reactants. 2 Mg(s) + O 2 (g) 2 MgO(s) Redox: the movement of electrons between reactants. Fig. 4.1 b The key event in a redox reaction is the movement of electrons between reactants. H 2 (g) + Cl 2 (g) 2 HCl(g) Balancing redox equations using oxidation numbers. The key concept in balancing a redox reaction is to make sure that the number of electrons lost by the reducing agent equals the number of electrons gained by the oxidizing agent. ___ Mg(s) + ___ O 2 (g) ___ MgO(s) Step 1: Assign oxidation numbers to all elements in the reaction. Step 4 of balancing redox equations using using ox #s The key concept in balancing a redox reaction is to make sure that the number of electrons lost by the reducing agent equals the number of electrons gained by the oxidizing agent. 2 Mg(s) + 1 O 2 (g) MgO(s) Step 1: Assign oxidation numbers to all elements in the reaction. Step 2: Identify the oxidized and reduced species. Step 3: Compute the number of electrons lost in the oxidation process and the number of electrons gained in the reduction process. (include all atoms undergoing oxidation or reduction!) (Draw tie-lines.) Step 4: Multiply one or both of these numbers by appropriate factors to make the electrons lost equal the electrons gained, and use the factors as stoichiometric balancing coefficients. Step 5: Complete the balancing by inspection, adding states of matter. Step 5 of balancing redox equations using using ox #s The key concept in balancing a redox reaction is to make sure that the number of electrons lost by the reducing agent equals the number of electrons gained by the oxidizing agent. 2 Mg(s) + 1 O 2 (g) 2 MgO(s) Step 1: Assign oxidation numbers to all elements in the reaction. Step 2: Identify the oxidized and reduced species. Step 3: Compute the number of electrons lost in the oxidation process and the number of electrons gained in the reduction process. (include all atoms undergoing oxidation or reduction!) (Draw tie-lines.) Step 4: Multiply one or both of these numbers by appropriate factors to make the electrons lost equal the electrons gained, and use the factors as stoichiometric...
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electrochemistry_fall2011_preclass - Electrochemistry 4.5:

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