13 of 15) Cold packs are often used by sports trainers to \"ice\" the njury of a

Question

13 of 15) Cold packs are often used by sports trainers to "ice" the njury of a player when ice-packs are not readily available. The cold pack consists of crystalline ammonium nitrate (NH4NO3) isolated from a ompartment of water. To initiate the cooling process the compartment of water is ruptured exposing it to the ammonium nitrate. The cold pack is then applied to the player's injury. Given this information predict the sign on each of the following thermodynamic quantities and give a brief explanation as to why the signs are as you stated:AG, ??, and ?S.

Explanation / Answer

The initial state of NH4NO3 is solid crystalline.

As soon as compartment is opened, NH4NO3 readily reacts with water to form final producst in liquid state.

So, state is changing from solid to liquid.

This gives delta S of reaction is positive.

(b)

The main process of this system is to give cold energy . This means removal of heat from surroundings. this is classic example of endothermic reaction where heat is taken from the surroundings and causes coldness for cold pack.

As we know endothermic reactions will have delta H as positive

(c)

delta G of this reaction will be negative as this reaction is very spontaneous at this temperature.As soon as compartment ruptures , reactions happen spontaneously.

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