Question

An ideal binary solution is prepared by using volatile components A and B. The total pressure of the solution is given by:
P = (200 - 100 $x_A$) mm of Hg
[$x_A$ represents the mole fraction of A in liquid phase]

Select the correct statement:

• A. Component A is more volatile
• B. Component B is more volatile
• C. Both components are equally volatile
• D. Cannot be predicted from given data

Answer 1

The correct option is B Component B is more volatile

More volatile component will have more vapor pressure in pure state at same temperature.

Given that

$P_T=200-100x_A$

where, $x_A$ = mole fraction of $A$

when, $x_A=1\Rightarrow$ Pure$A$ in liquid

$x_A=0\Rightarrow$ Pure$B$ in liquid

(1) $P_T(x_A=1)=P_A^0=(200-100\times 1)mm$

$=(200-100)mm$

$=100mm$

(2) $P_T(x_A=0)=P_B^0=(200-100\times 0)mm$

$=(200-0)mm$

$=200mm$

Since, $P_B^0>P_A^0$

$\therefore$ Component $B$ is more volatile then $A$