Thermodynamic properties of the RbF + RbBr + H2O and RbF + RbNO3 + H2O systems were determined by, the potentiometric method at the total ionic strengths ranging from 0.0017 to 0.7005 mol.kg(-1) for different ionic Strength fractions y(B) of RbBr/RbNO3 with y(B) = 0.00, 0.30, 0.60, and 0.90, at 298.2 K. Combining the Nernst equation and Pitzer equation, the mean ionic activity coefficients of RbF and RbBr/RbNO3, the osmotic coefficients, and the excess Gibbs energies of the studied systems were calculated.