Density profiles of chemically reacting fluids in slit-like pores

Abstract

A model of a chemically reacting fluid in a slit-like pore is studied. The density profiles of the fluid particles inside the pore, the adsorption isotherms, and the solvation force acting between the walls of the pore are investigated within the integral equation method. The Percus-Yevick and hypernetted chain approximations for the fluid particle-pore correlations are used. The model for the bulk chemically reacting fluid is that proposed by Cummings and Stell for a mixture of overlapping hard spheres. The investigations are performed for pores of different width, at different densities of the bulk fluid which is in an equilibrium with the confined fluid and for different degrees of bulk fluid association. The bulk fluid is described by using the Percus-Yevick approximation. A wide range of thermodynamic states and different bonding lengths between the reactants are investigated. It is shown that the effect of a chemical reaction in the bulk fluid produces qualitative changes in the behaviour of the density profiles of the particles of the system in the confined geometry, compared with the corresponding non-associated fluid. The effects of the bonding length between the reactants and the pore width influence the shape of the density profiles and their contact values. In particular, the contact density of a highly associated fluid is lower than unity for low packing fractions (densities), reflecting a decrease of the pressure, due to the associative interactions. This result has been obtained for the first time in the model of chemically reacting fluid within the singlet theory and coincides with the data for chain-like fluids in the slit-like pores obtained by using more sophisticated theories and computer simulation.