# Half reaction method justification

I have to say I have never really understood the half reaction method. What bothers me is that it seems to be too artificial. Too many little rules to remember! Why don't we use the mass conservation law to justify the process and use sistematically a set of linear equations to do the balances?

Because the two half-reactions need not necessarily occur at the same place and one half reaction can generally be substituted without affecting the other, it makes sense to think of them separately. This lets us do things like think about different lithium batteries. There are many types and they all use the $\ce{Li -> Li+ + e-}$ oxidation half-reaction, but it's coupled with different reduction half-reactions based on cobalt, iron, etc.