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Balancing Redox Equations. Many redox reactions are too complex to simply balance by inspection we must ensure that the e- lost and gained balance There are 2 methods to balance redox rxn: Half reaction Using oxidation numbers. Half Rxn Method. We’ll balance:
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Balancing Redox Equations • Many redox reactions are too complex to simply balance by inspection we must ensure that the e- lost and gained balance • There are 2 methods to balance redox rxn: • Half reaction • Using oxidation numbers
Half Rxn Method We’ll balance: Sn + HNO3 SnO2 + NO2 + H2O • Step 1: Assign oxidation numbers to each element to identify which is oxidized and which is reduced.
Step 2: write the half rxn, using only elements that change in oxidation number. Then add e- to balance the charges.
Step 3: Multiply each reaction by the lowest whole number so that e- lost = e- gained.
Step 4: Transfer the coefficients into the original reaction. • Step 5: Balance the remaining elements by inspection. • Step 6: Check the equation to see that it is balanced.
Balance the equation I2 + Cl2 + H2O HIO3 + HCl
Balance K2Cr2O7 + FeCl2 + HCl CrCl3 + KCl + FeCl3 + H2O
Balancing Acid/Base Solutions • We follow the same steps as before, but leave the H and O until the end, and then balance by adding H+, OH- or H2O according to: • In acid solutions, we add H+ and H2O as needed • In basic solutions we add OH- and H2O as needed
