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Most first aid "cold packs" are based on the endothermic dissolution of ammonium nitrate in water:

 

 

A particular cold pack contains 50.0 g of NH4NO3 and 125.0 g of water. When the pack is squeezed, the NH4NO3 dissolves in the water. If the pack and its contents are initially at 24.0oC, what is the lowest temperature that this bag could reach? (Assume that the ammonium nitrate solution has a specific heat of 4.25 J/gK and that the heat capacity of the bag itself is small enough to be neglected.)

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Christian Garcia
Christian GarciaLv10
11 Dec 2020

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Related questions

4. Instant cold packs are used for first aid when ice is not available. In one such device, a small pouch containing 2x102 grams of ammonium nitrate (NH4NO3) is placed in a bag containing 2x102 milliliters of water initially at 25oC. When the pouch is broken, ammonium nitrate dissolves in the water and the cold pack reaches a final temperature of -2oC. i). Calculate ∆Hos (kJ/mol NH4NO3) for the solution in the cold pack, assuming that the pack loses negligible amount of heat to the surroundings during the dissolution process and that the heat capacity of the solution is that of pure water. ii). What would be the final temperature (oC) of a pack containing 300 grams of ammonium nitrate and 300 ml of water? Show work

NH4NO3(s) + H2O(l) NH4NO3(aq) ?H = +25.7 kJWhat is the final temperature in a squeezed cold pack that contains 50.0 g of NH4NO3 dissolved in 135 mL of water? Assume a specific heat of 4.18 J/(g

The salt ammonium bromide dissolves in water according to the reaction:

 

(a) Calculate the standard enthalpy change ΔH° for this reaction, using the following data:

   

 

 

(b) Suppose 33.3 g of NH4Br is dissolved in 0.115 L of water at 23.5 °C. Calculate the temperature reached by the solution, assuming it to be an ideal solution with a heat capacity close to that of 115 g of pure water (specific heat = 4.18 J g-1 °C-1).

(c) Heats of reaction find practical application in hot packs or cold packs. Would this dissolution reaction be appropriate for the preparation of a hot pack or a cold pack?

 

 

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