The molality of a urea solution in which 0.0100 g of urea, $\left[{\left({\mathrm{NH}}_2\right)}_2\mathrm{CO}\right]$ is added to 0.3000 dm³ of water at STP is

Molality $=\frac{\text{Mass of moles of urea}}{\text{Mass of solvent}\left(\mathrm{in} \mathrm{ml}\right)}\times 1000$

Moles of urea $=\frac{0.6010}{60}\mathrm{mol}$

Water at STP $(\mathrm{d}=1\mathrm{g}/{\mathrm{cm}}^3=1\mathrm{kg}/{\mathrm{dm}}^3)=0.3{\mathrm{dm}}^3=0.3\mathrm{kg}$

$\therefore$ Molality $=\frac{0.010}{60\times 0.3}=5.55\times {10}^{-4}\mathrm{m}$