$$\Delta T_b = K_b \cdot m$$
where $\Delta T_b$ is the boiling point elevation, $K_b$ is the boiling point elevation constant of the solvent, and $m$ is the molality of the solution.
For water, $K_b$ is 0.512 °C/m. The molality of a 1 molar urea solution is:
$$m = \frac{1 \text{ mol urea}}{1 \text{ kg water}} = 1 \text{ mol/kg}$$
Therefore, the boiling point elevation of a 1 molar urea solution is:
$$\Delta T_b = 0.512 °C/m \cdot 1 \text{ mol/kg} = 0.512 °C$$
The boiling point of a 1 molar urea solution is therefore:
$$T_b = 100 °C + 0.512 °C = 100.512 °C$$
