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?

The enthalpy of the reaction is 18.616 kJ/mol.

Explanation:

Heat released by the solution = Q

Mass of the solution = 25.0 g

Heat capacity of the solution = c = 4.20 J/g K

Initial temperature of the solution ,

Final temperature of the solution,

Change in temperature of the solution = ΔT =

Heat gained during the reaction of ammonium nitrate = Q'

Q' = -Q (energy remained conserved)

Q'= -(-430.5 J)=430.5 J

Mass of ammonium nitrate added in water = 1.85 g

Moles of ammonium nitrate added in water =

0.02312 moles of ammonium nitrate absorbs 430.5 Joules of energy. the  1 mole will absorb:

The enthalpy of the reaction is 18.616 kJ/mol.

there are two significant figures.