Question

Dissolving 120 g of urea (mol. wt. 60) in 1000 g of water gave a solution of density 1.15 g/mL. The molarity of the solution is

• A. 1.78 M
• B. 2.00 M
• C. 2.05 M
• D. 2.22 M

Answer 1

The correct option is C 2.05 M

Molarity = $\frac{Molesofsolute}{Volumeofsolutions\left(L\right)}$
Moles of urea = $\frac{120}{60}=2$
Weight of solution = Weight of solvent + Weight of solute
= 1000 + 120 = 1120 g
$\Rightarrow Volume=\frac{1120g}{1.15g/mL}\times \frac{1}{1000mL/L}=0.973L$
$\Rightarrow Molarity=\frac{2.000}{0.973}=2.05M$