Echo W.

Key Skills

Freelancer Overview

CHAPTER Solution 2 Vapour Pressure F F F Ideal solution : 1 2 ⇒ DH = 0 Pressure exerted by vapours over the liquid surface at V T =V 1 +V 2 solution equilibrium. Non-Ideal Solutions T↑ ⇒ V.P.↑ (1) Solution showing +ve deviation : Attractive Forces↑ ⇒ V.P. ↓ F < F or F 1 2 Raoult’s Law V > V + V T 1 2 Q DH > 0 (1) Volatile binary liquid mix: solution Volatile liq. A B Mole fraction X / Y X / Y ⇒ liq/vapour A A B B V.P. of pure liq. Pº Pº A B Binary liquid solution: Pº A Pº B (cid:31) O X 1 A Fig.: A solution that shows +ve deviation from Raoult’s law By Raoult’s law ⇒ P = Pº X + Pº X = P + P ...(i) T A A B B A B (2) Solution showing -ve deviation: By Dalton’s law ⇒ P = Y P ...(ii) A A T ⇒ F > F and F P = Y P ...(iii) 1 2 B B T ⇒ V < (V + V ) T 1 2 Ideal and Non-Ideal Solutions ⇒ DH < 0 solution Ideal Solutions Solution-A Solution-B A.......A B.......B F F 1 2 V V 1 2 A.......B F V T Fig.: A solution that shows -ve deviation from Raoult’s law 2 Table: Deviation from Raoult’s Law where n = mole of Non-volatile solute. B Negative i = Van’t Hoff’s factor. Positive deviation Zero deviation deviation (DH = +ve) (DH = 0) (DH = – ve) (2) Elevation in B.P. : acetone + D T = (T′ – T ) = i. K × m. (i) ethanol + cyclohexane benzene + toluene b b b b chloroform RT2 where K = b acetone + carbon benzene + n-hexane + b 1000×l (ii) v disulphide chlorform n-heptane where T = B.P. of pure solvent. b nitric acid + ehyl bromide + (iii) acetone + benzene l= Latent heat of vapourization (per gm