The boiling point of aqueous solutions depend on the nature of intermolecular interactions present. KBr will yield an ionic solution but NH3 will yield a molecular solution having hydrogen bonds. The degree of hydrogen bonding in the aqueous solution will further increase with the concentration of the solution.
Remember that experimental data shows that hydrogen bonds are strong bonds that lead to a significant increase in the boiling point of solutions. Hence 0.1M NH3 solution will have a higher boiling point due to intermolecular hydrogen bonding in the solution.
