The study of molecular interactions of ascorbic acid and sodium ascorbate with water at temperatures (278.15, 288.15 and 298.15) K

Abstract

The article reports experimental values of density (ρ), speed of sound (u), viscosity (η) and refractive index (nD) for the binary systems, (L-ascorbic acid+water) and (sodium ascorbate+water) over the concentration range (0.01 to 0.75)mol·kg−1 at temperatures (T=278.15, 288.15 and 298.15)K. From these experimental results, apparent molar volume Vϕ of solute, isentropic compressibility of solution κS, apparent molar isentropic compressibility κϕ of solute and relative viscosity of solution (ηr) have been calculated. The limiting apparent molar volume Vϕ0 of solute, limiting apparent molar isentropic compressibility κϕ0, limiting apparent molar expansivity Eϕ0 of solute, coefficient of thermal expansion (α∗) and hydration number (nH) of water soluble vitamins have been obtained. The experimental values of relative viscosity were used to calculate Falkenhagen coefficient A and Jones–Dole coefficient B. The transition state theory has been used to calculate the Gibbs free energy of activation of viscous flow per mole of solvent (Δμ10#) and per mole of solute (Δμ20#). The related activation parameters like ΔS20# and ΔH20#have also been calculated. From the results obtained, a discussion was carried out in terms of interactions and structure factor (in the framework of “structure-making” and “structure-breaking” solutes) in these binary mixtures.