Question

The plot of $P_T$ vs $X_A$ at constant temperature in the pressure composition diagram is
$P_T\to \text{Total pressure}$
$X_A\to \text{Mole fraction of A in liquid phase}$

Answer 1

Pressure composition phase diagram is the superimpose plot of $P_T$ vs $Y_A$ (curve) and $P_T$ vs $X_A$ (straight line).

The plot of $P_T$ vs $X_A$ give a straight line and it represented by the equation,
$P_T=(P_A^0-P_B^0)X_A+P_B^0$
Its in form of $y=mx+c$
$Slope=(P_A^0-P_B^0)$
$\text{y-intercept}=P_B^0$