Name: Non-ideal Solutions
Uploaded: 2019-07-19
Duration: 8 min 43 s
Description: We know that an ideal solution is a theoretical concept. So, what are non-ideal solutions? Why do they show a deviation from Raoult's law? Let's explore!

Question

The vapour pressure of pure liquids A and B are

450

and

700 mm Hg

respectively, at

350 K

. Find out the composition of the liquid mixture if total vapour pressure is

600 mm Hg

. Also find the composition of the vapour phase.

Accepted Answer

${P_{A}}^{0} = 450 mm, {P_{B}}^{0} = 700 mm, P_{TOTAL} = 600 mm$

According to Raoult's law,

$P_{total} = P_{A} + P_{B} = x_{A} {P^{0}}_{A} + x_{B} {P^{0}}_{B} = x_{A} {P^{0}}_{A} + (1 - x_{A}) {P^{0}}_{B} = X_{A} {P^{0}}_{A} + {P^{0}}_{B} - {P^{0}}_{B} X_{A} = {P^{0}}_{B} + X_{A} ({P^{0}}_{A} - {P^{0}}_{B}) 600 = 700 + (450 - 700) x_{A} x_{A} = 0.40 x_{B} = 1 - 0.40 = 0.60 P_{A} = x_{A} {P^{0}}_{A} = 0.40 \times 450 = 180 mm P_{B} = x_{B} {P^{0}}_{B} = 0.60 \times 700 = 420 mm$

Mole fraction of A in vapour phase $= \frac{P_{A}}{P_{A} + P_{B}} = \frac{180}{180 + 420} = 0.30$

Mole fraction of B is $= 1 - 0.30 = 0.70$

NCERT Solutions for Chapter: Solutions, Exercise 3: Intext Questions

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