A liquid mixture of benzene and toluene is composed of 1 mol of benzene and 1 mol of toluene. If the pressure over the mixture is reduced for vapourisation of liquid mixture. (P° Toluene = 32.0 mm of

Question

A liquid mixture of benzene and toluene is composed of 1 mol of benzene and 1 mol of toluene. If the pressure over the mixture is reduced for vapourisation of liquid mixture.

(P°_Toluene = 32.0 mm of Hg, P°_Benzene = 112 mm of Hg) ?

List - I	List - II
(P) The vapour pressure of first vapour form is	(1) 49.78
(Q) Vapour pressure of the system when last trace of liquid will disappear is	(2) 59.87
(R) Vapour pressure of the system when half of total amount of liquid will vapourise	(3) 72
(S) Composition at pressure at pressure 59.87 mmHg (approx.)	(4) $x_{T} = 0.5$
	(5) $x_{T} = 0.65$

TestHub · Accepted Answer

x T ​ , x B ​ are the mole fractions of liquid Toluene and Benzene, respectively. y T ​ , y B ​ are the mole fractions of vapor of Toluene and Benzene, respectively. (P) The vapor pressure of the first vapor formed is: P t o t a l ​ = x T ​ P T ∘ ​ + x B ​ P B ∘ ​ = 0.5 × 32 + 0.5 × 112 = 72 mm H g (Q) The vapor pressure of the system when the last trace of liquid disappears is: P t o t a l ​ 1 ​ = 32 1 ​ + ( 112 1 ​ − 32 1 ​ ) × 0.5 = 49.78 mm H g (R) The vapor pressure of the system when half of the total amount of liquid has vaporized is: P t o t a l ​ = P T ∘ ​ × P B ∘ ​ ​ = 32 × 112 ​ = 59.87 mm H g (S) 59.87 = x T ​ × 32 + ( 1 − x T ​ ) × 112 , 59.87 = 32 x T ​ + 112 − 112 x T ​ 59.87 − 112 = − 80 x T ​ − 52.13 = − 80 x T ​ x T ​ = − 80 − 52.13 ​ = 0.65

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