Which of the following changes decreases the vapour pressure of water kept in a sealed vessel?

The mass of non-volatile,non-electrolyte solute (molar mass $= 50 \ g \ mol^{-1}$) needed to be dissolved in $114 \ g$ octane to reduce its vapour pressure to $75\%$ is .............. $g$.

Calculate the relative lowering of vapour pressure of a solution containing $46 \ g$ of non-volatile solute in $162 \ g$ of water at $20^{\circ} C$. [Molar mass of non-volatile solute $= 46 \ g \ mol^{-1}$]

The vapour pressure lowering caused by the addition of $100 \, g$ of sucrose (molecular mass $= 342$) to $1000 \, g$ of water if the vapour pressure of pure water at $25 \, ^oC$ is $23.8 \, mm \, Hg$.

Vapour pressure of a solution of benzene $(P^o_{benzene} = 120 \ torr)$ and toluene $(P^o_{toluene} = 80 \ torr)$ having $2 \ moles$ of each is ......... $torr.$

At $30^\circ C$,liquid $A$ and $B$ form an ideal solution. The total vapor pressure of a solution containing $1 \ mol$ of $A$ and $2 \ mol$ of $B$ is $250 \ mm \ Hg$. The total vapor pressure becomes $300 \ mm \ Hg$ when $1 \ mol$ more of $A$ is added to the first solution. What are the vapor pressures of pure $A$ and $B$ at the same temperature?