2. Guidelines 1)Write down overall equation. 2)Determine oxidation and reduction half-reactions. 3)Balance the atoms.  Add H 2 O to balance oxygens.  Add H + ions to balance hydrogens. 4)Balance the charges.  Add electrons here. 5)Balance the half-reactions based on electron number  need to have the same amount for oxidation and reduction. 6)Add the half-reactions and simplify.

3. Example 2:Example 2:  Balance the following reaction occurring in an acidic solution.  HNO 2  NO 2

4. Example 3:Example 3:  Balance the following reaction occurring in an acidic solution.  Cr 2 O 7 -2 + Cl -  Cr +3 + Cl 2

5. Example 4:Example 4:  Balance the following reaction occurring in an acidic solution.  Zn + NO 3 - → Zn +2 + N 2 O

7. How do we recognize redox reactions occurring in basic solutions?  Hydroxide ions (OH - ) present instead of H + ions  How do we balance this redox reaction????  Treat equation like a reaction occurring in an acidic solution  Add hydroxide ions (OH - ) to equal the H + amount for the ENTIRE equation. Add OH - ions to BOTH sides ! ! !  If equal number of OH - and H + ions on one side, combine into H 2 O molecules

8. Example 1:Example 1:  A disproportion occurs with Br 2 in a basic solution.  Hint: balance redox equation normally until “Step 6: simplifying the overall equation”  What in the world is a disproportion?  Disproportion reaction---  A type of redox reaction where the same chemical substance is both oxidized and reduced.

9. Classwork  Balancing Redox Reactions Worksheet  #5—8 on “More Practice with Redox Reactions” Worksheet

10. Homework  pp. 792 #27-29