An element (atomic weight $=250 \mathrm{u}$ ) crystallises in a simple cubic lattice. If the density of the unit cell is $7.2 \mathrm{~g} \mathrm{~cm}^{-3}$. What is the radius (in $\mathop {\rm{A}}\limits^{\rm{o}}$ ) of the atom of the element?
$$ \left(N_A=6.02 \times 10^{23} \mathrm{~mol}^{-1}\right) $$
1.95 g of non-volatile and non-electrolyte solute dissolved in 100 g of benzene lowered the freezing point of it by 0.64 K .
The molar mass of the solute (in $\mathrm{g} \mathrm{mol}^{-1}$ )
$$ \left(K_f\left(\mathrm{C}_6 \mathrm{H}_6\right)=5.12 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right) $$
At $298 \mathrm{~K}, 0.714$ moles of liquid $A$ is dissolved in 5.555 moles of liquid $B$. The vapour pressure of the resultant solution is 475 torr. The vapour pressure of pure liquid $A$ at the same temperature is 280.7 torr. What is the vapour pressure of pure liquid $B$ in torr?
The resistance of a conductivity cell filled with 0.1 M KCl solution is $100 \Omega$. If the resistance of the same cell when filled with 0.2 M KCl solution is $520 \Omega$, the molar conductivity of 0.02 M solution (in $\mathrm{S} \mathrm{cm}^2 \mathrm{~mol}^{-1}$ ) is (Given: conductivity of 0.1 M KCl solution $=1.29 \mathrm{Sm}^{-1}$ )
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