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BALANCING REDOX EQUATIONS (from Dr. Raynor) We will investigate the rules for balancing redox reactions by applying these rules to the following chemical reaction Fe2+ + Cr2O72- ---> Fe3+ + Cr3+, in both acidic and basic solution. 1. Determine Substance Oxidized and Substance Reduced and Write in Separate Half-Reactions: First, determine which substance is being oxidized and which is being reduced. Separate them into two separate half-reactions: one for oxidation and one for reduction. In our example, Fe is being oxidized, (going from +2 to +3), and Cr is being reduced, (going from +6 in Cr2O72- to +3 in Cr+3). Our half-reactions are thus Fe2+ ---> Fe3+ oxidation half-reaction Cr2O72- ---> Cr3+ reduction half-reaction 2. Balance All Elements Except O and H: The first reaction is fine as is, but the second needs to have the Cr atoms balanced. After this step our two reactions are as follows: Fe2+ ---> Fe3+ oxidation half-reaction Cr2O72- ---> 2Cr3+