The molality of a 10% (v/v) solution of di-bromine solution in $\mathrm{CCl}_{4}$ (carbon tetrachloride) is 'x'. $x =$ ______ $\times 10^{-2}$ M. (Nearest integer) [Given: molar mass of $\mathrm{Br}_{2} = 160~\mathrm{g~mol}^{-1}$, atomic mass of C = $12~\mathrm{g~mol}^{-1}$, atomic mass of Cl = $35.5~\mathrm{g~mol}^{-1}$, density of dibromine = $3.2~\mathrm{g~cm}^{-3}$, density of $\mathrm{CCl}_{4} = 1.6~\mathrm{g~cm}^{-3}$]

JEE Main · 2023 · 01 Feb 2023 · Shift 2 · Some Basic Concepts of Chemistry

The molality of a 10% (v/v) solution of di-bromine solution in

CCl_{4}

(carbon tetrachloride) is 'x'.

x =

______

\times 1 0^{- 2}

M. (Nearest integer)
[Given: molar mass of

Br_{2} = 160 g mol^{- 1}

, atomic mass of C =

12 g mol^{- 1}

, atomic mass of Cl =

35.5 g mol^{- 1}

, density of dibromine =

3.2 g cm^{- 3}

, density of

CCl_{4} = 1.6 g cm^{- 3}

]

Answer: 139

In a ten per cent volume solution,

10

mL of dibromine is present in

100

mL of solution, leaving

90

mL of carbon tetrachloride as the solvent. The mass of dibromine is

10 \times 3.2 = 32

g, which is

\frac{32}{160} = 0.2

mol, and the mass of solvent is

90 \times 1.6 = 144

g, that is

0.144

kg. The molality is

\frac{0.2}{0.144} = 1.39

mol kg

^{- 1}

, which is

139 \times 1 0^{- 2}

mol kg

^{- 1}

JEE Main · 2023 · 01 Feb 2023 · Shift 2 · Integer answer