Mass of Urea $(NH_2CONH_2)$ required to be dissolved in $1000 \ g$ of water to reduce the vapour pressure of water by $25 \ \%$ is $...... \ g$. (Nearest integer) Given: Molar mass of $N, C, O$ and $H$ are $14, 12, 16$ and $1 \ g \ mol^{-1}$ respectively.

Two liquids $A$ and $B$ form an ideal solution. At $320 \ K$, the vapour pressure of the solution, containing $3 \ mol$ of $A$ and $1 \ mol$ of $B$ is $500 \ mm \ Hg$. At the same temperature, if $1 \ mol$ of $A$ is further added to this solution, the vapour pressure of the solution increases by $20 \ mm \ Hg$. The vapour pressure (in $mm \ Hg$) of $B$ in the pure state is . . . . . . (Nearest integer).

Find the molar mass of solute when $2 \ g$ is dissolved in $60 \ g$ of benzene,and the relative lowering of vapour pressure is $0.06$. (Molar mass of benzene is $78 \ g \ mol^{-1}$)

What is the vapour pressure of a solution containing $0.1 \ mol$ of solute dissolved in $1.8 \times 10^{-2} \ kg$ of $H_2O$ (in $mm \ Hg$)? $(P_1^0 = 24 \ mm \ Hg)$

Vapour pressure of chloroform $(CHCl_{3})$ and dichloromethane $(CH_{2}Cl_{2})$ at $298\,K$ are $200\,mm\,Hg$ and $415\,mm\,Hg$ respectively. $(i)$ Calculate the vapour pressure of the solution prepared by mixing $25.5\,g$ of $CHCl_{3}$ and $40\,g$ of $CH_{2}Cl_{2}$ at $298\,K$ and,$(ii)$ mole fractions of each component in vapour phase.

The variation of vapour pressure $(b)$ as a function of temperature $(a)$ is studied for $C_2H_5OC_2H_5$,$CCl_4$,and $H_2O$ at $760 \ mm \ Hg$ and is shown in the figure below. The boiling temperatures of $C_2H_5OC_2H_5$,$CCl_4$,and $H_2O$ are $308 \ K$,$350 \ K$,and $373 \ K$ respectively. Curves $A$,$B$,and $C$ respectively correspond to: