For an ideal solution, it perfectly obeys Raoult's law over the entire range of concentrations, meaning the observed vapour pressure matches the pressure calculated by Raoult's law ($\Delta P = 0$). Furthermore, the intermolecular attractive forces between the components (A-B) are nearly equal to those in the pure components (A-A and B-B). This results in zero enthalpy of mixing ($\Delta H_{\text{mix}} = 0$) and zero volume of mixing ($\Delta V_{\text{mix}} = 0$). However, the mixing of two miscible liquids is a spontaneous process that leads to an increase in the randomness or disorder of the system. Therefore, the entropy of mixing is always positive ($\Delta S_{\text{mix}} > 0$) and is never equal to zero.