Do acetone-aniline solution give positive deviation from Roult's law ?
No, acetone-aniline solution shows negative deviation from Roult's law.
Explanation for negative deviation.
When acetone and aniline are mixed there are new attractive forces due intermolecular hydrogen bonding between acetone oxygen and aniline hydrogen attached to Nitrogen. Thus, the attractive forces become stronger and the escaping tendency of each liquid from the solution decrease. Therefore the vapour pressure is less than that expected for an ideal solution.
In such solutions,∆mixingH and ∆mixingV are not equal to zero as explained:
(i)∆mixingH is negative because energy is released due to increase in attractive forces. Therefore, dissolution process is exothermic.
(ii) Because of the increase in forces of attraction in the solution, the molecules will held more tightly. therefore, there will be decrease in volume on mixing, i.e∆mixingV will be negative.
Explanation for negative deviation.
When acetone and aniline are mixed there are new attractive forces due intermolecular hydrogen bonding between acetone oxygen and aniline hydrogen attached to Nitrogen. Thus, the attractive forces become stronger and the escaping tendency of each liquid from the solution decrease. Therefore the vapour pressure is less than that expected for an ideal solution.
In such solutions,
(i)
(ii) Because of the increase in forces of attraction in the solution, the molecules will held more tightly. therefore, there will be decrease in volume on mixing, i.e