Urine odor gets worse with time because urine contains the metabolic product urea [CO(NH2)2], a compound that is slowly converted to ammonia and carbon dioxide:




This reaction is much too slow for the enthalpy change to be measured directly using a temperature change. Instead, the enthalpy change for the reaction may be calculated from the following data:

Compound ΔH°f (kJ/mol)
Urea(aq) –319.2
CO2(aq) –412.9
H2O(l) –285.9
NH3(aq) –80.8