Question

Density of $3\,M$ solution of $NaCl$ is $1.25 \,g/mL$ The mass of the solvent in the solution is

• A. $1075.4 \,g$
• B. $10.745 \,g$
• C. $10.754\, g$
• D. $1074.5\, g$

Answer 1

Answer: (D)

$1074.5\, g$

Answer 2

$d = {1.25\, g/mL}$, conc, of solution = 3 M
= 3 moles in one litre of the solution.
Molar mass of ${NaCl = 23 + 35.5 = 58.5 \, g \,mol^{-1}}$
Volume of solution= 1 L = 1000 mL
Mass of solution = $d \times V$
= ${1.25\, g mL^{-1} \times 1000\, mL}$
= 1250 g
Mass of solute (NaCl) = n $\times$ molar mass
= ${ 3 \times 58.5 : 175.5 \,g}$
Mass of solvent
= Mass of solution - mass of solute
= 1250 -175.5 = 1074.5 g