Instant cold packs 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 endothermic reaction: nh4no3 (s) --> nh4+ (aq) + no3- (aq) 1.85g ammonium nitrate is added to water in a calorimeter. the total solution (water and ammonium nitrate) is 25.0g. the heat capacity of the calorimeter is ccal=45.0 j/k. the initial temperature of the solution is 21.1c. the final temperature of the solution is 17.0c. assume cs of the solution is 4.20 j/(g k) what is δhrxn per mol of the reaction?