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

In which of the following Galvanic cells emf is maximum?

(Given, $E_{\mathrm{Mg}^{2+} \mid \mathrm{Mg}}^{\circ}=-2.36 \mathrm{~V}$

and $E_{\mathrm{Cl}_2 \mid 2 \mathrm{Cl}^{-}}^{\circ}=+136 \mathrm{~V}$ )

Isomerisation of gaseous cyclobutene to butadiene is first order reaction. At $T(\mathrm{~K})$. The rate constant of reaction is $33 \times 10^{-4} \mathrm{~s}^{-1}$. What is the time required (in min ) to complete $90 \%$ of this reaction at the temperature? $(\log 2=03)$