Question

The molarity of $H_{2}S{O}_4$ is $18M$. Its density is $1.8gm{L}^{-1}$. Hence, molality is :

• A. 36 m
• B. 200 m
• C. 500 m
• D. 18 m

Answer 1

The correct option is C 500 m

The molarity of $H_{2}S{O}_4$ is 18 M.
Hence, 1 L of $H_{2}S{O}_4$ corresponds to 18 moles of $H_{2}S{O}_4$.
The density of $H_{2}S{O}_4$ is 1.8 g/mL.
Thus 1 L of $H_{2}S{O}_4$ corresponds to 1800 g or 1.8 kg.
Out of this $18\times 98=1.764kg$ corresponds to $H_{2}S{O}_4$.
Hence, the mass of water is $1.8kg-1.764kg=0.036kg$.
Hence, the molality of the solution is $\frac{18}{0.036}=500m$.