When an ideal solution is formed process is spontaneous. According to Raoult's law, for an ideal solution, ∆H=0,∆Vmix =0. Since, there is no exchange of heat energy between system and surroundings. i.e. ∆SSystem =+ ve ⇒∆SSurrounding =0 For the relation; Gibbs free energy; ∆G=∆H−T∆S ∆G=(0)−(+) ∆G=− ve (for spontaneous process) Hence, ∆G=− ve, ∆H=0,∆SSystem =+ ve, ∆SSurrounding =0