Writing Half Equations For Acidic and Basic Aqueous Solutions Tutorial
To write a balanced oxidation or reduction reaction for a species in aqueous solution:
- Write a skeletal equation for the oxidation or reduction equation based on the information provided.
- Balance the half-reaction equation according to the following sequence:
(i) Balance all atoms other than H and O by inspection
(ii) Balance O atoms by adding H2O to the appropriate side
(iii) Balance the H atoms.
The way this is done depends on whether the solution is acidic or basic (alkaline):
(A) Acidic Solution:
Add the appropriate number of H+ to the side deficient in H
(B) Basic (alkaline) Solution:
Add one H2O molecule to the side deficient in H
add one OH- ion to the opposite side, for each H atom needed.
You may need to cancel out H2O molecules duplicated on both sides of the equation at this point.
(iv) Balance the charge by adding electrons (e-) to the side deficient in negative charge.