Cold packs, whose temperatures are lowered when ammonium nitrate dissolves in water, are carried by athletic trainers when trans
porting ice is not possible. Which of the following is true of this reaction? a. ΔH < 0, process is exothermic
b. ΔH > 0, process is exothermic
c. ΔH < 0, process is endothermic
d. ΔH > 0, process is endothermic
e. ΔH = 0, since cold packs are sealed
Cold packs contain ammonium nitrate (NH₄NO₃). When this salt dissolves in water, it decreases the temperature of the surroundings. This happens because the process is endothermic (absorbs heat from the surroundings). By convention, when a process is endothermic, the standard enthalpy carries a positive sign (ΔH° > 0).
