For gas-liquid reaction systems with inlet and outlet streams, this paper proposes a linear transformation to decompose the numbers of moles vector into five distinct parts, namely, the extents of reaction, the extents of mass transfer, the extents of inlet flow, the extents of outlet flow, and invariants. Furthermore, several implications of being able to compute the extents of reaction, mass transfer, and inlet flow are discussed. The concept is illustrated via the simulation of various reactor configurations for the chlorination of butanoic acid.