Models play an important role in understanding chemical engineering systems. While differential equation models are taught in standard modeling and control courses, Differential Algebraic Equation (DAE) system models are not usually introduced. These models appear naturally in several chemical engineering problems. In this paper, the introduction of DAE systems in undergraduate and graduate curriculum is proposed through a simple reactive flash example. This is a useful chemical engineering example that combines the equilibrium and reaction concepts in a simple unit. This example can logically follow a flash example that is typically taught in the thermodynamics class. This example can also be included in a modeling or mathematical methods class.