Question

The molality of a $10 \%$ (v/v) solution of di-bromine solution in $CCl _4$ (carbon tetrachloride) is ' $x$ ' $x=$____ $\times 10^{-2} M$ (Nearest integer) [Given : molar mass of $Br _2=160 \,g \,mol ^{-1}$ atomic mass of $C =12\, g \,mol ^{-1}$ atomic mass of $Cl =355\, g\, mol ^{-1}$ density of dibromine $=32 \,g\, cm ^{-3}$ density of $CCl _4=16\, g \,cm ^{-3}$ ]

Answer 1

Correct Answer: 139

The correct answer is 139.
( $10ml$ solute in $90ml$ solvent
mass of solute $=10\times 3.2=32g$
mass of solvent $=90\times 1.6g$
$m=\frac{32\times 1000}{160\times 90\times 1.6}=1.388$
$m-138.8\times 10^{-2}-139$