20.2 Balancing Redox Equations

Half-Reaction Method

Used to balance redox equations

Treat the oxidation and reduction as two seperate processes, balance them, and them combine them to attain the balanced equation for the overall reaction.

Assign oxidation numbers

To determine what is oxidized and what is reduced.

Write the oxidation and reduction half-reactions

Description

For acidic solution

First balance elements other than H and O.

Then balance O by adding H₂O

Next, balance H atoms by adding H⁺ atoms

Finally, balance charges by adding electrons.

Multiply the half-reactions by integers

So that the electrons gained and lost are the same.

Add the half reactions, make sure equation is balanced according to mass and charge

Description

Balance each half-reaction

Description

For basic solution

First balance elements other than H and O.

Then balance O by adding H₂O

Next, balance H atoms by adding H⁺ atoms

Then, balance charges by adding electrons.

Finally, since the solution is basic, add OH^- each side of the half reaction for every H⁺.