Question

Which of the following is true for a binary immiscible solution?
$P_A^0$ is the vapour pressure of component A in pure state
$P_B^0$ is the vapour pressure of component B in pure state
$n_X$ are number of moles of component ‘X’ present in the vapour phase

• A. $\frac{P_A^0}{P_B^0}=\frac{n_A}{n_B}$
• B. $\frac{P_B^0}{P_A^0}=\frac{n_A}{n_B}$
• C. $\frac{P_A^0}{P_B^0}={\left(\frac{n_A}{n_B}\right)}^2$
• D. ${\left(\frac{P_A^0}{P_B^0}\right)}^2=\frac{n_A}{n_B}$

Answer 1

The correct option is A $\frac{P_A^0}{P_B^0}=\frac{n_A}{n_B}$

Immiscible Liquids
The total vapour pressure is the sum of the separate vapour pressures of the two components in the pure state at the given temperature.
$P_A=P_A^0$
$P_A=P_B^0$
$P_T=P_A^0+P_B^0$

$P_A^0=\frac{n_{A}RT}{V}$
$P_B^0=\frac{n_{B}RT}{V}$
Dividing above equations
$\frac{P_A^0}{P_B^0}=\frac{n_A}{n_B}$