In this paper, we study the steady state behavior of an isobaric, adiabatic reactive flash for a binary mixture. The presence of vapor-liquid equilibrium can remove or create multiple steady states. For example, a system that does not have multiple steady states in a one-phase CSTR can display multiple steady states as a two-phase reactive flash unit. Both steady state input multiplicity (i.e., multiple values of input resulting in one value of output) and output multiplicity (i.e., one value of input resulting in multiple values of output) are possible. The existence of multiple steady states and their stability properties are related to a dimensionless quantity, Lambda, that depends on the heats of reaction and vaporization as well as the compositions in the system. The results are illustrated in several examples.