For a particular redox reaction NO2– is oxidized to NO3– and Cu2 is reduced to Cu . Complete and balance the equation for this reaction in basic solution. Phases are optional.
To balance the redox equation in basic solution, you need to follow these steps:
Step 1: Write down the unbalanced equation.
NO2– + Cu2+ → NO3– + Cu
Step 2: Separate the equation into two half-reactions: one for the oxidation reaction and one for the reduction reaction.
Oxidation half-reaction: NO2– → NO3–
Reduction half-reaction: Cu2+ → Cu
Step 3: Balance the atoms in each half-reaction, excluding oxygen and hydrogen.
Oxidation half-reaction: 4NO2– → 4NO3–
Reduction half-reaction: Cu2+ → Cu
Step 4: Balance the oxygen atoms by adding water (H2O) to the side lacking oxygen.
Oxidation half-reaction: 4NO2– → 4NO3– + 2H2O
Reduction half-reaction: Cu2+ → Cu
Step 5: Balance the hydrogen atoms by adding hydrogen ions (H+) to the side lacking hydrogen.
Oxidation half-reaction: 4NO2– + 2H2O → 4NO3– + 4H+
Reduction half-reaction: Cu2+ → Cu
Step 6: Balance the charge on each half-reaction by adding electrons (e–) to the appropriate side of the equation.
Oxidation half-reaction: 4NO2– + 2H2O → 4NO3– + 4H+ + 2e–
Reduction half-reaction: Cu2+ + 2e– → Cu
Step 7: Multiply each half-reaction by an appropriate number to ensure that the electrons cancel out.
Oxidation half-reaction: 4NO2– + 2H2O → 4NO3– + 4H+ + 2e– (Multiply by 2)
Reduction half-reaction: Cu2+ + 2e– → Cu (Leave as is)
Step 8: Combine the half-reactions, ensuring that the number of electrons cancel out.
Add both half-reactions:
8NO2– + 4H2O + Cu2+ → 8NO3– + 4H+ + Cu
Step 9: Check the equation to verify that the atoms and charges are balanced.
The equation should now be balanced in basic solution.