In principle any balance, be it in baking a cake, accounting, electrical engineering, mechanical engineering or chemical engineering is suppose to be simple, but for some reason maths always find a way to complicate things a little. So lets get the balance going. The general balance for any thing in life is as follows: EQ1: General Balance equation Before trying to visualize the math, lets first try and understand the hardware we are trying to describe mathematically. This is what a PFR (Plug Flow Reactor) looks like. FIG1: Plug Flow Reactor And this is how we are going to graphically illustrate a plug flow reactor. FIG2: Mole balance of species i in dv with these images in mind, lets try and explain the mathematics that describes it, by taking the mole balance and substituting values that is of importance to the system we obtain: EQ2: General Mole Balance with F i0 and F i being the initial and final feed rates respectively in [moles/time], G i being gain [mo