Liquid Solution

In a mixture of liquids $A$ and $B$, if the mole fractions of component $A$ in vapour phase and liquid mixture are $x_1$ and $x_2$ respectively, then the total vapour pressure of liquid mixture is

(Where $p_{\mathrm{A}}^0$ and $p_{\mathrm{B}}^0$ are the vapour pressure of pure $A$ and $B$ )