Post on 18-Jan-2016
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