nstant cold packs sometimes used to treat athletic injuriescontain solid ammonium nitrate and liquid water separatedbya thindivider. When the divider is broken, the ammonium nitrate dissolvesendothermically:
NH4NO3(s) ïƒ NH4+(aq) + NO3–(aq)
To measure the enthalpy of this reaction, you dissolve 1.25 g ofammonium nitrate in enough water to make 25.0 mL of solution. Theinitial temperature is 25.8 °C, and the final temperature is 21.9°C. (Assume that the density of the solution is 1.00 g /mL and thatthe heat capacity of the solution is 4.184 J/g∙°C
