The half reaction method of balancing chemical equations has severe disadvantages compared to alternative methods. It is difficult to define a half reaction exactly, and thus to define a corresponding mathematical concept. Furthermore, existence and uniqueness proofs of the solutions (balanced chemical equations) require advanced mathematics. Thus the method demands chemical rote learning instead of general reasoning. Therefore, it is not expedient as a method of balancing chemical equations, and it gives a poor ‘explanation’ of the oxidation number balancing method.