A solution of A and B with 30 moles present of A is in equilibrium with its vapour which contain 60 mole percent of A. Assuming that the solution and the vapour behave ideally, calculate the ratio of the vapour pressures of pure A and pure B.

A solution of A and B with 30 moles present of A is in equilibrium wit

1.	A solution of A and B with 30 moles present of A is in equilibrium with its vapour which contain 60 mole percent of A. Assuming that the solution and the vapour behave ideally, calculate the ratio of the vapour pressures of pure A and pure B.
Answer» Solution :`{:("In solution",x_(A)=0.30, therefore, x_(B)=0.70),("In the vapour phase,",y_(A)=0.60,therefore,y_(B)=0.40):}` But`y_(A)=(p_(A))/("TOTAL V.P.")=(p_(A))/(p_(A)+p_(B))=(x_(A)p_(A)^(@))/(x_(A)p_(A)^(@)+x_(B)p_(B)^(@))=(0.30p_(A)^(@))/(0.30p_(A)^(@)+0.70p_(B)^(@))=0.60"...(i)"` `y_(B)=(p_(B))/(p_(A)+p_(B))=(x_(B)p_(B)^(@))/(x_(A)p_(A)^(@)+x_(B)p_(B)^(@))=(0.70p_(B)^(@))/(0.30p_(A)^(@)+0.70p_(B)^(@))=0.40"...(II)"` Dividing EQN. (i) by eqn. (ii), `(0.30p_(A)^(@))/(0.70p_(B)^(@))=(0.60)/(0.40) or (p_(A)^(@))/(p_(B)^(@))=(0.60)/(0.40)xx(0.70)/(0.30)=3.5`