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

The following graph is obtained for vapour pressure (in atm) (on $Y$-axis) and $T$ (in K) (on $X$-axis) for aqueous urea solution and water. What is the boiling point (in K) of urea solution?

(Atmospheric pressure $=1 \mathrm{~atm}$ )