Solid ammonium nitrate is used in a cold-pack demonstration. In a laboratory trial, 5.00 g of NH4NO3 is added to 100.0 g of water initially at 24.0 °C in a perfectly insulated coffee-cup calorimeter. The temperature of the resulting solution decreases to 20.1 °C.
Assume the solution density is 1.00g mL−1 and the specific heat capacity of the solution is 4.18J g−1∘C−1. The molar mass of NH4NO3 is 80.04 g mol−1.
(a) Calculate the quantity of heat, q, absorbed or released by the contents of the calorimeter. Include the correct sign and units.
(b) Determine the number of moles of NH4NO3 that dissolved.
(c) Using your answers from parts (a) and (b), determine the molar enthalpy change, ΔH, for the dissolution of NH4NO3 under the conditions of this experiment. Report your answer with appropriate units and sign.
(d) State whether the dissolution of NH4NO3 is exothermic or endothermic and justify your answer with reference to the calculated ΔH value.