Determination of correct molecular mass from Raoult's law is applicable to

For which of the following liquid mixtures $\Delta_{\text{mix}}H=0$ and $\Delta_{\text{mix}}V=0$?

Two liquids $A$ and $B$ form an ideal solution. When they are mixed in a molar ratio of $1:1$,the vapor pressure of the solution at $300 \ K$ is $400 \ mm \ Hg$. When they are mixed in a molar ratio of $1:2$,the vapor pressure of the solution at the same temperature is $350 \ mm \ Hg$. The vapor pressures of pure liquids $A$ and $B$ are respectively:

When acetone is added to chloroform,then a hydrogen bond is formed between them. These liquids show:

Two liquids $A$ and $B$ form an ideal solution at temperature $T \ K$. At $T \ K$,the vapour pressures of pure $A$ and $B$ are $55 \ kNm^{-2}$ and $15 \ kNm^{-2}$ respectively. What is the mole fraction of $A$ in the solution of $A$ and $B$ in equilibrium with a vapour in which the mole fraction of $A$ is $0.8$?

In a binary ideal solution of liquids $A$ and $B$ at a constant temperature,the mole fraction of $B$ in the liquid phase is $0.4$ and in the vapor phase is $0.25$. If $P_B^o = 40 \ mm \ Hg$,then the vapor pressure of pure liquid $A$ at that temperature is .......... $mm \ Hg$.