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Ideal solutions
Question

Vapour pressure of pure A is 70 mm of Hg at 25oC.It forms an ideal solution with 'B' in which mole fraction of A is 0.8. If the vapour pressure of the solution is 84 mm of Hg at 25oC the vapour pressure of pure B at 25oC is

Easy
Solution

Given,pA=70mmHg xA=0.8
 xB=(10.8)=0.2 and p=84mmHg
According to Raoult's law,
                                          p=pAxA+pBxB84=0.8×70+0.2×pBpB=280.2=140mmHg
 

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