Question

Urea on reaction with water gives ?
A: ${\text{N}}{{\text{H}}_3}$
B: ${{\text{N}}_2}{{\text{O}}_3}$
C: ${\text{HN}}{{\text{O}}_2}$
D: ${\text{HN}}{{\text{O}}_3}$

Answer 1

Hint: Reaction of urea with water gives 2 gaseous products as in this case one gaseous product formed is of 2 moles while other is just 1 mole.

Complete answer:
Reaction of urea with water:
${\text{N}}{{\text{H}}_2}{\text{CON}}{{\text{H}}_2} + {{\text{H}}_2}{\text{O}} \to {\text{2N}}{{\text{H}}_3} + {\text{C}}{{\text{O}}_2}$
Gases evolved here are:
Carbon Dioxide
Ammonia

Hence option A is the correct answer.

Additional Information:
1.Urea is soluble in water because of hydrogen bonding between urea and water molecules.
${\text{N}}{{\text{H}}_2}{\text{CON}}{{\text{H}}_2}$, this is the chemical formula of urea. In this because of high electronegativity of oxygen atom, this becomes partially negative and there is partial positive charge on carbon atom. Thus, the hydrogen atom of water molecules forms hydrogen bonds with partially negatively charged oxygen atoms of urea.
2.Addition of urea on water decreases the freezing point because freezing-point depression is the decrease of the freezing point of a solvent in addition to a non-volatile solute.
The freezing point is the temperature at which the vapor pressures of liquid solvent and solid solvent are equal. When a non-volatile solute is added to a volatile liquid solvent, the solution vapor pressure will be lower than that of the pure solvent. As a result the solid will reach equilibrium with the solution at a lower temperature than with the pure solvent.
Urea dissolves in its own weight in water, but becomes increasingly difficult to dissolve as the concentration increases. Dissolving urea in water is endothermic—the solution temperature falls when urea dissolves.

Note:
Students should always remember to keep the reaction balanced if in case ,it was asked to name that gas whose 2 moles are formed per mole of urea.
Reaction of urea with water shows colligative property ,that is, depression in freezing point.