The vapour pressure of pure liquids 1 and 2 are 550mmHg and 800mmHg respectively at 350K.
What will be the mole fraction of component 2 in liquid phase when total vapour pressure of the solution is 600mmHg?
A
0.1
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B
0.2
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C
0.9
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D
0.8
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Solution
The correct option is B0.2 By Raoult's Law : PT=p∘1χ1+p∘2χ2
where PT is the total pressure of the solution. p∘1 is the vapour pressure of pure component 1 p∘2 is the vapour pressure of pure component 2 χ1 is the mole fraction of component 1 in liquid phase. χ2 is the mole fraction of component 2 in liquid phase.
Putting the values: 600=550χ1+800χ2600=550χ1+800(1−χ1)600=800−250χ1χ1=0.8 χ2=1−0.8=0.2