277479 Vapour pressure of pure ' $A$ ' is $70 \mathrm{~mm} \mathrm{of} \mathrm{Hg}$ at $20^{\circ} \mathrm{C}$. It forms an ideal solution with ' $B$ ' in which mole fraction of $A$ is 0.8 . If the vapour pressure of the solution is $84 \mathrm{~mm}$ of $\mathrm{Hg}$ at $25^{\circ} \mathrm{C}$, the vapour pressure of pure ' $B$ ' at $25^{\circ} \mathrm{C}$ is
277479 Vapour pressure of pure ' $A$ ' is $70 \mathrm{~mm} \mathrm{of} \mathrm{Hg}$ at $20^{\circ} \mathrm{C}$. It forms an ideal solution with ' $B$ ' in which mole fraction of $A$ is 0.8 . If the vapour pressure of the solution is $84 \mathrm{~mm}$ of $\mathrm{Hg}$ at $25^{\circ} \mathrm{C}$, the vapour pressure of pure ' $B$ ' at $25^{\circ} \mathrm{C}$ is
277479 Vapour pressure of pure ' $A$ ' is $70 \mathrm{~mm} \mathrm{of} \mathrm{Hg}$ at $20^{\circ} \mathrm{C}$. It forms an ideal solution with ' $B$ ' in which mole fraction of $A$ is 0.8 . If the vapour pressure of the solution is $84 \mathrm{~mm}$ of $\mathrm{Hg}$ at $25^{\circ} \mathrm{C}$, the vapour pressure of pure ' $B$ ' at $25^{\circ} \mathrm{C}$ is
277479 Vapour pressure of pure ' $A$ ' is $70 \mathrm{~mm} \mathrm{of} \mathrm{Hg}$ at $20^{\circ} \mathrm{C}$. It forms an ideal solution with ' $B$ ' in which mole fraction of $A$ is 0.8 . If the vapour pressure of the solution is $84 \mathrm{~mm}$ of $\mathrm{Hg}$ at $25^{\circ} \mathrm{C}$, the vapour pressure of pure ' $B$ ' at $25^{\circ} \mathrm{C}$ is