Molecular mass of \(\left[\left( NH _{2}\right)_{2} CO \right]=60 g / mol\)

\(\therefore\) No. of moles \(=\frac{0.0100}{60.06}=1.67 \times 10^{-4} mol\)

Now, Mass \(=\) Volume \(\times\) Density

Density of water \(=10^{3} g / dm ^{3}\) and Volume \(=0.3000 dm ^{3}\)

\(\therefore\) Mass of water \(=0.3000 \times 10^{3}=300 g =0.3 kg\)

Molality \(=\frac{\text { Moles of solute }}{\text { Mass of solvent(kg) }}=\frac{1.67 \times 10^{-4}}{0.3}=5.57 \times 10^{-4} m\)