The vapour pressure of a pure liquid A is 70 torr at 27° C . It forms an ideal solution with another liquid B. The mole fraction of B is 0.2 and total vapour pressure of the solution in 84 torr at 27° C . The vapour pressure of pure liquid B at 27° C is

Question

The vapour pressure of a pure liquid A is 70 torr at 27° C . It forms an ideal solution with another liquid B. The mole fraction of B is 0.2 and total vapour pressure of the solution in 84 torr at 27° C . The vapour pressure of pure liquid B at 27° C is (A) 140 torr (B) 56 torr (C) 14 torr (D) 70 torr

Tardigrade Admin · Accepted Answer

According to Raoult's law, p=pAo.XA+pBo.XB Here pAo=70 text torr,XA=1-XB=1-0.2=0.8,p=84 text torr, XB=0.2 and pBo=? So 84 torr =70 text torr× text0.8+ textpBo× 0.2 or pBo=(84 text torr - 56 text torr/0.2)=140 text torr .

Q. The vapour pressure of a pure liquid A is 70 torr at $2 7^{\circ} C$ . It forms an ideal solution with another liquid B. The mole fraction of B is 0.2 and total vapour pressure of the solution in 84 torr at $2 7^{\circ} C$ . The vapour pressure of pure liquid B at $2 7^{\circ} C$ is

140 torr

56 torr

14 torr

70 torr

According to Raoult's law, $p = p_{A}^{o} . X_{A} + p_{B}^{o} . X_{B}$

Here $p_{A}^{o} = 70 torr, X_{A} = 1 - X_{B} = 1 - 0.2 = 0.8, p = 84 torr, X_{B} = 0.2$ and $p_{B}^{o} = ?$

So 84 torr $= 70 torr \times 0.8+ p_{B}^{o} \times 0.2$

or $p_{B}^{o} = \frac{84 torr - 56 torr}{0.2} = 140 torr$ .

Q. The vapour pressure of a pure liquid A is 70 torr at 27∘C . It forms an ideal solution with another liquid B. The mole fraction of B is 0.2 and total vapour pressure of the solution in 84 torr at 27∘C . The vapour pressure of pure liquid B at 27∘C is