Balancing Redox Reactions

1
Balancing Redox Reactions
2
Steps

1. Assign oxidation numbers
2. Write half reactions
3. Balance electrons to determine coefficients needed

3

Problem 1
2 -2 0 0
2HgO ? O2 2Hg
Hg2 2e- ? Hg0
Reduction
O-2 ? O0 2e-
Oxidation
4

Problem 2
1 5 -2 1 -1 0
2KClO3 ? 2KCl 3O2
6e- Cl5 ? Cl-1
Reduction
3(O-2 ? O0 2e-)
Oxidation
5

Problem 3
1 -1 0 2 -1 0
2HCl Zn ? ZnCl2 H2
2e- 2H1 ? H20
Reduction
Zn0 ? Zn2 2e-
Oxidation
6

Problem 4
1 5 -2 0 2 5 -2
0
2Ag NO3 Cu ? Cu(NO3)2 2Ag
2e- 2Ag1 ? 2Ag0
Reduction
Cu0 ? Cu2 2e-
Oxidation
7

Problem 5
-3 1 0 0 1 -2
4NH3 3O2 ? 2N2 6H2O
12e- 3O20 ? 6O-2
Reduction
4N-3 ? 2N20 12e-
Oxidation
8

Problem 6
0 3 5 -2 0
2 5 -2
3Mg 2Al(NO3)3 ? 2Al 3Mg(NO3)2
6e- 2Al3 ? 2Al0
Reduction
3Mg0 ? 3Mg2 6e-
Oxidation
9

Problem 6
0 3 2 0
3Ca 2Al3 ? 3Ca2 2Al
6e- 2Al3 ? 2Al0
Reduction
3Ca0 ? 3Ca2 6e-
Oxidation
10

Problem 7
2Fe3 Sn2 ? 2Fe2 Sn4
2e- 2Fe3 ? 2Fe2
Reduction
Sn2 ? Sn4 2e-
Oxidation
11

Problem 8
1 5 -2 2 -1 1 -1 2
-2 4 -1 1 -2
2HNO3 3MnCl2 6HCl ? 2NO 3MnCl4 4H20
6e- 2N5 ? 2N2
Reduction
3Mn2 ? 3Mn4 6e-
Oxidation
12

Problem 9
1 6 -2 1 -1 0
1 -2 3 -1 1 -1
K2(Cr2O7) 14HCl ? 3Cl2 7H2O 2CrCl3 2KCl
6e- Cr26 ? 2Cr3
Reduction
6Cl-1 ? 3Cl20 6e-
Oxidation