Question

At a given temperature, total vapour pressure in Torr of a mixture of volatile components $A$ and $B$ is given by $P=120-75 X_{B}$ 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

$P_{s}=120-75 x_{B}...(2)$

From $(1) \&(2)$

$P_{A}^{\circ}=120, P_{B}^{\circ}-P_{A}^{\circ}=-75$

$P_{B}^{\circ}-120=-75$

$P_{B}^{\circ}=45$.