Balancing Redox Reactions under Basic Conditions

Balancing Redox Reactions under Basic Conditions 

balancing redox equations can involve quite a lot of bookkeeping. Not much can be done to remedy that unfortunate fact. But here s the good news The process for balancing redox equations under basic conditions is 90 percent identical to the one used for balancing under acidic conditions in the preceding section. In other words, master one, and you ve mastered both. 

Here s how easy it is to adapt your balancing method for basic conditions  

Perform Steps 1-7 as described in the preceding section for balancing under acidic conditions. 

Observe where H is present in the resulting equation. Add an identical amount of OH to both sides of the equation so that all the H+ is neutralized, becoming water. 

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Balancing Redox Reactions under Basic Conditions... 

Here s a summary of the method for balancing a redox reaction equation for a reaction under acidic conditions (excess H+) (see the next section for details on balancing a reaction under basic conditions) ... 

In solving this problem the major effort was to balance a redox equation for a reaction under basic conditions. This allowed us to find the molar relationship between dithionite and chromate ions. The remainder of the problem was a stoichiometry calculation for a reaction in solution, much like Example 4-10 (page 127). A quick check of the final result involves (1) ensuring that the redox equation is balanced, and (2) noting that the number of moles of Cr04 is about 1.5 (i.e., 100 X 0.0148), that the number of moles of 8204 is about 2.25 (i.e., 1.5 X 3/2), and that the mass of Na2S204 is somewhat more than 350 (i.e., 2.25 X 175). 

Follow the nine steps for balancing a redox reaction equation under basic conditions ... 

You have seen many balanced chemical equations and net ionic equations that represent redox reactions. There are specific techniques for balancing these equations. These techniques are especially useful for reactions that take place under acidic or basic conditions, such as the acidic conditions used in coating a master CD with silver. 

Redox reactions do not always take place under neutral conditions. Balancing half-reactions is more complicated for reactions that take place in acidic or basic solutions. When an acid or base is present, or OH ions must also be considered. However, the overall approach is similar. This approach involves writing the correct formulas for the reactants and products, balancing the atoms, and adding the appropriate number of electrons to one side of the half-reaction to balance the charges. 

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