Balancing Redox Reactions

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Balancing Redox
Half Reaction
 Each redox reaction can be divided into two parts:
one for oxidation, the other reduction
 These parts are called half-reactions
 Ex. – Break into two half-reactions
Ce4+ + Sn2+  Ce3+ + Sn4+
Balancing Redox
 Atoms and charges must be balanced
 Balance the acidic redox reaction below
H+ + Cl- + Sn + NO3-  SnCl62- + NO2 + H2O
Step 1 For Balancing
 Determine oxidation states for all atoms in the
reaction
+1
-1
0
+5 -2
+4 -1
+4 -2
+1 -2
H+ + Cl- + Sn + NO3-  SnCl62- + NO2 + H2O
Step 2
 Show electrons gained and lost using “tie lines”
1 e- gained
+1
-1
0
+5 -2
+4 -1
+4 -2
+1 -2
H+ + Cl- + Sn + NO3-  SnCl62- + NO2 + H2O
4 e- lost
Step 3
 Use coefficients to equalize the electrons gained and
lost
+1
-1
0
+5 -2
+4 -1
+4 -2
+1 -2
H+ + Cl- + Sn + 4NO3-  SnCl62- + 4NO2 + H2O
Step 4
 Balance the rest by inspection
8H+ + 6Cl- + Sn + 4NO3-  SnCl62- + 4NO2 + 4H2O
Sample
 Balance the redox reaction below
PbO + NH3 → N2 + H2O + Pb

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