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 $B$ )

Two liquids ' $A$ ' and ' $B$ ' form an ideal solution. At 300 K , the vapour pressure of a solution containing 1 mole of ' $A$ ' and 3 moles of ' $B$ ' is 550 mm Hg . At the same temperature, if one more mole of ' $B$ ' is added to the solution, the vapour pressure of solution increases to 560 mm Hg . Then the ratio of vapour pressures of $A$ and $B$ in their pure state is

Which one of the following mixtures can be separated by steam distillation technique?

Observe the following data given in the table ( $K_H=$ Henry's law constant)

$$ \begin{aligned} &\begin{array}{ccccc} \hline \text { Gas } & \mathrm{CO}_2 & \mathrm{Ar} & \mathrm{HCHO} & \mathrm{CH}_4 \\ \hline\left(\boldsymbol{K}_{\mathrm{H}} \text { bar at } \mathbf{2 9 8 ~ K}\right) & 1.67 & 40.3 & 1.83 \times 10^{-5} & 0.413 \\ \hline \end{array}\\ &\text { The correct order of their solubility in water is } \end{aligned} $$