1. 2.6 Redox Part 1a. Balancing Redox Reactions (Half-equation method)
b. write ionic half-equations and use them to construct full ionic equations.
Connector:
Updated_Crowe_2012

3. Balancing Redox Reactions (Half-equation method)
The half-equation method separates a redox reaction into its oxidation and reduction half reactions.
Overall scheme for the half reaction method:
Step 1: Split reaction into half-reactions (reduction and oxidation)
Step 2: Balance the charge or oxidation number with electrons
Step 3: Balance O by adding H2O
Step 4: Balance H by adding H+
Step 5: Multiply by some integer to make electrons (lost) = electrons (gained)
Step 6: Add half equations and cancel substances on both sides

4. Example 1.
Reaction between manganese (II) ion and the bismuthate ion in acid solution 2+ 5+ 7+ 3+
What are the oxidation numbers for Mn and Bi ?
Write the half equation for Mn 2+
Balance O by adding H2O, then H by adding H+
Repeat the process for the bismuthate ion

5. Balance O by adding H2O, then H by adding H+
We now have the two half equations:
Step 5: Multiply by some integer to make electrons (lost) = electrons (gained)
Step 6: Add half equations and cancel substances on both sides

6. 8 2 2 16 10 10 30 5 5 15
Step 6: Add half equations and cancel substances on both sides

7. Overview

8. Solve these acid solution reactions: :
MnO4-  Mn 2+
2 I-  I2
H2O2  H2O + O2
Cr2O72-  Cr3+

9. 8H+ + MnO4– + 5Fe3+ ➔ 5Fe2+ + Mn2+ + 4H2O
Cr2O72- + 3H2O2 + 8H+  2Cr3+ + 3O2 +7H2O