This video explains with an example how to perform material balance on systems that involve more than one reaction. Problem was done first by using atomic species balance and then by using extent of reaction. It was demonstrated that the use of molecular species balance, when multiple reactions are involved, is error prone because of the estimation of so many generation and consumption terms. In contrast to that, the other two methods are simple and straightforward to use. The problem taken is an unsolved problem of Himmelblau, section 10.1.