Question

The density of $3M$ solution of sodium chloride is $1.252\, g\, mL^{-1}$. The molality of the solution will be: (molar mass, $NaCl = 585\, g\, mol^{-1}$)

• A. 260 m
• B. 2.18 m
• C. 2.79 m
• D. 3.00 m

Answer 1

Answer: (C)

2.79 m

Answer 2

The relation between molarity (M) and molality (m) is
$d=M\left(\frac{1}{m}+\frac{M_{2}}{1000}\right), M_{2}=$ Mol. mass of solute
On putting value
$1.252=3\left(\frac{1}{m}+\frac{58.5}{1000}\right)$
on solving $m = 2.79$