We present a coupled thermodynamically-consistent framework for the reactive chemo-mechanical responses of solid solutions. Specifically, we focus on chemically active solid solutions subject to mechanical effects due to heterogeneous stresses distributions, where the stress generation process (pressure) is driven solely by volume changes associated with the chemical processes. Throughout this paper, we use the model to describe common geological processes. Furthermore, simulation results of a three-phases solid solution provide insights into the phenomena and verify the interleaving between the physical and chemical interactions at solid-state. In particular, we show the evolution of the thermodynamic pressure as the system goes to the steady state.