Material balance involves calculations the quantities of all materials that enter and leave any system or process which are based on the principle of the “law of conversation of mass”. This law states that matter is neither created nor destroyed in the process and the total mass remains unchanged. The general principle of material balance calculations is to put and solve a number of independent equations involve number of unknowns of compositions and mass flow rates of streams enter and leave the system or process. The process can be defined as one or a series of operations in which physical and chemical treatments are carried out and a desired product is result in the end such as distillation, drying, absorption, chemical manufacture, … etc. The system can be defined as any arbitrary portion of a process that you want to consider for analysis such as a reactor. The system boundary must be fixed in each problem by drawing an imaginary boundary around it as shown in the following figure: