Balancing Redox rx

Steps to balancing in an acidic solution.

1. Write half-reactions without including electrons.

2. Balance the number of all atoms except oxygen and hydrogen.

3. Balance oxygen atoms by adding water molecules.

4. Balance hydrogen atoms by adding H+

5. Balance charge by adding electrons.

6. Equalize electrons in the half-reactions by multiplication.

7. Combine the two half reactions.

8. Check to see that atoms and charges balance.

Cu + NO3- → Cu2+ + NO

• Balance the reaction:

• Write the two half reactions

– Cu → Cu2+

– NO3- → NO

– Cu → Cu2+ There is no oxygen or hydrogen in this

reaction, so leave it alone.• Balance oxygen using water

– NO3- → NO + 2 H2O

Balance hydrogen using H+

– 4 H+ + NO3- → NO + 2 H2O

– Balance charge by adding electrons

– Cu → Cu2+ + 2e-

– 3e- + 4 H+ + NO3- → NO + 2

H2O

• Equalize the electrons

• Lowest common multiple is 6

3[Cu → Cu2+ + 2e-]

2[3e- + 4 H+ + NO3- → NO + 2 H2O]

Multiple each species by the multiple so that the electrons are equal in both half reactions.

3 Cu → 3 Cu2+ + 6e-

6e- + 8 H+ + 2 NO3- → 2 NO + 2 H2O

____________________________________3 Cu + 8 H+ + 2 NO3

- → 3 Cu2+ + 2 NO + 2 H2O

Anything that existsas a product and as a reactant can be crossed off