How do you use the half-equation to represent oxidation-reduction reactions?
The half equation method features the loss or or gain of electrons as ACTUAL particles in order to balance redox equations.
Let's represent the oxidation of aluminum to give alumina,
This ionic species features
In each redox equation, charge and mass is conserved, as it must be.
In the final equation, we wish to eliminate electrons, because these are hypothetical particles: so we cross-multiply,
Now this was simply a combustion reaction, which is intuitively easy to solve. Try the oxidation of elemental sulfur to
Balance the oxygens (using water)
Now balance the hydrogens:
Again, both mass and CHARGE are balanced, as required. We need a corresponding reduction reaction to ACCEPT the electrons.
Another reaction, oxidation of ammonia to nitric oxide:
Is this reaction balanced with respect to mass and charge? Why?