How do I do this? Instant cold packs, often used to ice athletic njuries on the

Question

How do I do this? Instant cold packs, often used to ice athletic njuries on the field, contain ammonium nitrate and water separated by a thin plastic divider When the divider is broken, the ammonium (titrate dissolves according to the fottowmg endothemic reaction NH+4NO,(aq) NH+4 (aq) +NO_ (aq) In order to m g easure the enthalpy change for this reaction. 1.25 of NH_4NO_3 is dissolved in enough water to make 25.0 mL of solution The initial temperature is 25.8 C and the final temperature (after the solid dissolves) is 21. 9 degree C.Calculate the change enthalpy for the reaction in kilojoules per mote (Use 1.0 g/ mL as the derail of the solution and 1.18 J /g. degree C as the pocific heat capacity) Express your answer to two significant figures and includc tho appropriate units.

Explanation / Answer

No of mol of NH4NO3 = 1.25/80.0434 = 0.0156 mol

solution = 25 ml

mass of solution = 25*1 = 25 grams

q absorbed = 25*4.18*(25.8-21.9) = 407.55 joule

    = 0.407 kj

dHrxn = 0.407/0.0156 = 26.1 kj/mol

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