Question

At a given temperature, total vapour pressure in Torr of a mixture of volatile components $A$ and $B$ is given by $P=120-75X_B$ hence, vapour pressure of pure $A$ and $B$ respectively (in Torr) are -

• A. 120,75
• B. 120,195
• C. 120,45
• D. 75,45

Answer 1

Answer: (C)

$P_s=P_A^{\circ }\cdot x_A+P_B^{\circ }\cdot x_B$

$=P_A^{\circ }\left(1-x_B\right)+P_B^{\circ }\cdot x_B$

$P_s=P_A^{\circ }+x_B\left(P_B^{\circ }-P_A^{\circ }\right)...(1)$

given equation

$P_s=120-75x_B...(2)$

From $(1)\&(2)$

$P_A^{\circ }=120,P_B^{\circ }-P_A^{\circ }=-75$

$P_B^{\circ }-120=-75$

$P_B^{\circ }=45$.