At $300 \mathrm{~K}, 6 \mathrm{~g}$ of urea was dissolved in 500 mL of water. What is the osmotic pressure (in atm) of resultant solution?

$$ \begin{aligned} & \left(R=0.082 \mathrm{~L}^{\operatorname{atm~K}}{ }^{-1} \mathrm{~mol}^{-1}\right) \\ & (\mathrm{C}=12 ; \mathrm{N}=14 ; \mathrm{O}=16 ; \mathrm{H}=1) \end{aligned} $$

Benzoic acid undergoes dimerisation in benzene. $x \mathrm{~g}$ of benzoic acid (molar mass $122 \mathrm{~g} \mathrm{~mol}^{-1}$ ) is dissolved in 49 g of benzene. The depression in freezing point is 1.12 K . If degree of association of acid is $88 \%$. What is the value of $x$ ? $\left(K_f\right.$ for benzene $\left.=4.9 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right)$

At $T(\mathrm{~K})$ two liquids $A$ and $B$ form an ideal solution. The vapour pressures of pure liquid $A$ and $B$ at that temperature are 400 and 600 mm Hg respectively, If the mole fraction of liquid $B$ is 0.3 in the mixture, the mole fractions of $A$ and $B$ in vapour phase respectively are