Question

Find the molarity and molality of a 15% (w/w) $H_{2}S{O}_4$ solution.
(Density of the solution is 1.10 g/mL)

• A. 1.53 M, 1.64 m
• B. 1.68 M, 1.68 m
• C. 1.80 M 1.68 m
• D. 1.68 M 1.80 m

Answer 1

The correct option is D 1.68 M 1.80 m

15% (w/w) $H_{2}S{O}_4$ $\Rightarrow 15g{H}_{2}S{O}_4$ in 100 g of solution
$\Rightarrow$ 150 g $H_{2}S{O}_4$ in 1000 g solution
$Volumeofthesolution=\frac{\text{Mass}}{\text{density}}=\frac{1000}{1.10}=909mL\text{Molarity}=\frac{\text{Number of moles of Solute}}{\text{volume of solution in L}}$
$\Rightarrow \frac{150\times 1000}{98\times 909}=1.68M\text{Mass of solvent}=1000-150=850g\text{Molality}=\frac{\text{Number of moles of solute}}{\text{Mass of solvent in kg}}$
$\Rightarrow \frac{150\times 1000}{98\times 850}=1.80$ m