Instant cold packs, often used to ice athletic injuries on the field, contain ammonium nitrate and water separated by a thin plastic divider. When the divider is broken, the ammonium nitrate dissolves according to the following endothermic reaction:

In order to measure the enthalpy change for this reaction, 1.25g of is dissolved in enough water to make 25.0ml of solution. The initial temperature is 25.8C and the final temperature (after the solid dissolves) is 21.9C

Calculate the change in enthalpy for the reaction in kilojoules per mole. (Use 1.0g/ml as the density of the solution and 4.184 J/g*C as the specific heat capacity.)