The molality of a 10%(v/v) solution of di-bromine solution in CCl₄ (carbon tetrachloride) is ‘x’
x =_________ x10^-2 M (Nearest integer)
[Given : molar mass of ${\mathrm{Br}}_2=160 {\mathrm{g} \mathrm{mol}}^{-1}$
Atomic mass of Cl = 35.5 g mol^-1
Density of dibromine = 3.2 g cm^-3
Density of $\left.{\mathrm{CCl}}_4=1.6\mathrm{g}{\mathrm{cm}}^{-3}\right]$

$10\mathrm{\%}\frac{\mathrm{V}}{\mathrm{V}}$ solution of Br₂ in CCl₄ means 10 mL of Br₂ is present in 100 mL of solution.
Weight of CCl₄ in 100 mL of the solution.
$\begin{array}{l}=90\times 1.6\\ =144\mathrm{g}\end{array}$
Weight of Br₂ in 100 mL of solution
$\begin{array}{l}=10\times 3.2\mathrm{g}\\ =32\mathrm{g}\end{array}$
Molality $=\frac{32}{160}\times \frac{1000}{144}\mathrm{mol}\cdot {\mathrm{kg}}^{-1}$
              $\begin{array}{l}=1.38888\text{ mol }.{\mathrm{kg}}^{-1}\\ =139\times {10}^{-2}\mathrm{mol}.{\mathrm{kg}}^{-1}\end{array}$
               $\cong 139\times {10}^{-2}\mathrm{mol}.{\mathrm{kg}}^{-1}$