Thermodynamic study of the aqueous rubidium and manganese bromide system

Crystallization of 2RbBr . MnBr2 . 2H(2)O, the only double salt obtained un der standard conditions from saturated aqueous rubidium-manganese bromide s olutions, was theoretically predicted using the "hard" and "soft" Lewis aci ds and bases concept and Pauling's rules. The RbBr-MnBr2-H2O system was the rmodynamically simulated by the Pitzer model assuming a solubility diagram of three branches only: RbBr, 2RbBr . MnBr2 . 2H(2)O and MnBr2 . 4H(2)O. Th e theoretical result was experimentally proved at 25 degrees C by the physi cochemical analysis method and formation of the new double salt 2RbBr . MnB r2 . 2H(2)O was established. It was found to crystallize in a triclinic cry stal system, space group -Pl, a = 5.890(1) Angstrom, b = 6.885(1) Angstrom, c = 7.367(2) Angstrom, alpha = 66.01(1)degrees, beta = 87.78(2)degrees,gam ma = 84.93(2)degrees, V = 271.8(1) Angstrom(3), Z = 1, D-x = 3.552 g-cm(-3) . The binary and ternary ion interaction parameters were calculated and the solubility isotherm was plotted. The standard molar Gibbs energy of the sy nthesis reaction, Delta(r)G(m)degrees of the double salt 2RbBr . MnBr2 . 2H (2)O from the corresponding simple salts RbBr and MnBr2 . 4H(2)O, as well a s the standard molar Gibbs energy of formation, Delta(f)G(m)degrees, and st andard molar enthalpy of formation Delta(f)H(m)degrees of the simple and do uble salts were calculated.