Question

Dissolving $120\, g$ of a compound (mol. wt $= 60$) in $1000\, g$ of water gave a solution of density $1.12\, g \, mL^{-1}$. The molarity of solution is

• A. 1.0 M
• B. 2.0 M
• C. 2.5 M
• D. 4.0 M

Answer 1

Answer: (B)

2.0 M

Answer 2

Given, density $(d)=1.12\, g\, mL ^{-1}$

Mass of solute $(w)-120\, g$

Molar mass of solute $(M)=60$

Mass of solvent $(w)=1000\, g =1000\, mL$

$\therefore$ Total mass $=1000+120=1120\, g$

$\because d=\frac{\text { Mass }}{\text{Volume}(V)}$

$\therefore$ Total volume $(V)=\frac{1120}{1.12}=1000\, mL$

$\because$ Molarity $(c)=\frac{w}{M} \times \frac{1000}{V}$

$\because$ Molarity $(c)=\frac{w}{m} \times \frac{1000}{1000}=\frac{120}{60}=2.0\, m$