The Total pressure observed by mixing two liquid A and B is 350 mm Hg when their mole fractions are 0 . 7 and 0 . 3 respectively. The Total pressure becomes 410 mm Hg if the mole fractions are changed

Question

The Total pressure observed by mixing two liquid A and B is 350 mm Hg when their mole fractions are 0 . 7 and 0 . 3 respectively. The Total pressure becomes 410 mm Hg if the mole fractions are changed to 0 . 2 and 0 . 8 respectively for A and B . The vapour pressure of pure A is ______ mm Hg . (Nearest integer) Consider the liquids and solutions behave ideally

TestHub · Accepted Answer

Let Vapour pressure of pure A be P A o Let Vapour pressure of pure B be P B o Using Raoult's law and Dalton's law: When X A = 0 . 7 & X B = 0 . 3 P s = 350 ⇒ P A o × 0 . 7 + P B o × 0 . 3 = 350 . . . . ( i ) When X A = 0 . 2 & X B = 0 . 8 P s = 410 ⇒ P A o × 0 . 7 + P B o × 0 . 3 = 350 . . . . ( ii ) Solving ( i ) and ( ii ) P A o = 314 mm Hg P B o = 434 mm Hg

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