Q.

Consider a binary solution of two volatile liquid components 1 and 2. x1 and x2 are the mole fractions of component 1 in liquid and vapor phase, respectively. The slope and intercept of the linear plot of 1x1 vs 1y1 are given respectively as:               [2025]

1 P10P20, P20-P10P20  
2 P10P20, P10-P20P20  
3 P20P10, P10-P20P20  
4 P20P10, P20-P10P20  

Ans.

(1)

Vapour pressure of component 1 in solution (P1)=P1°x1-(A)  [Raoult’s law]

Vapour pressure of component 2 in solution (P2)=P2°x2  [Raoult’s law]

Total vapour pressure of solution (PT)=P1+P2=P1°x1+P2°x2  [Dalton’s law]

PT=P1°x1+P2°x2=P1°x1+P2°(1-x1)=(P1°-P2°)x1+P2°

Also, vapour pressure of component 1 in solution (P1)
=PTy1=[(P1°-P2°)x1+P2°]y1-(B)  [Dalton’slaw]

Equating (A) and (B)

P1°x1=[(P1°-P2°)x1+P2°]y1

P1°y1=[(P1°-P2°)x1+P2°]x1

P1°y1=(P1°-P2°)+P2°x1

P2°x1=P1°y1+(P2°-P1°)

1x1=P1°P2°×1y1+(P2°-P1°)P2°