Name: Expressing Concentration by Mass Percent
Uploaded: 2019-07-19
Duration: 3 min 32 s
Description: Mass percentage is a way of representing the concentration of an element in a compound or a component in a mixture. Let us learn more through this video.

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

Given :- $P_{A}^{0} = 450 mm, P_{B}^{0} = 700 mm, P_{T} = 600 mm$

According to Raoult's law,

$P_{total} = P_{A} + P_{B}$

$= X_{A} P_{A}^{0} + X_{B} P_{B}^{0}$

$= X_{A} P_{A}^{0} + (1 - X_{A}) P_{B}^{0}$

$= X_{A} P_{A}^{0} + P_{B}^{0} - P_{B}^{0} X_{A}$

$= P_{B}^{0} + X_{A} (P_{A}^{0} - P_{B}^{0})$

$600 = 700 + (450 - 700) X_{A}$

$X_{A} = 0.40$

$X_{B} = 1 - 0.40 = 0.60 P_{A} = X_{A} P_{A}^{0} = 0.40 \times 450 = 180 mm P_{B} = X_{B} P_{B}^{0} = 0.60 \times 700 = 420 mm$

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 $= 1 - 0.30 = 0.70$

Telangana Board Solutions for Chapter: Solutions, Exercise 3: Intext Questions

Telangana Board Chemistry Solutions for Exercise - Telangana Board Solutions for Chapter: Solutions, Exercise 3: Intext Questions

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