If two substances $A$ and $B$ have $P_A^o : P_B^o = 2 : 1$ and have mole fraction in solution $1 : 3$,then the mole fraction of $A$ in the vapour phase is:

The vapour pressure of a liquid depends on

The vapour pressure of pure benzene and toluene are $160 \ torr$ and $60 \ torr$ respectively. The mole fraction of toluene in the vapour phase in contact with an equimolar solution of benzene and toluene is:

$1 \ mol$ each of the following solutes are taken in $5 \ mol$ of water:
$(i) \ NaCl$
$(ii) \ K_2SO_4$
$(iii) \ Na_3PO_4$
$(iv) \ \text{glucose}$
Assuming $100 \%$ ionization of the electrolytes,the relative decrease in vapor pressure will be in the order:

The relative lowering of the vapour pressure is equal to the ratio between the number of

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.