Adding 4.88 g of NH4NO3(s) to 140 g of water in a coffee-cup calorimeter (with stirring to dissolve the salt) resulted in a decrease in temperature from 19.0 °C to 16.7 °C. Calculate the enthalpy change for dissolving NH4NO3(s) in water in kJ/mol. Assume the solution (whose mass is 144.9 g) has a specific heat capacity of 4.2 J/g K. (Cold packs take advantage of the fact that dissolving ammonium nitrate in water is an endothermic process.) A cold pack uses the endothermic enthalpy of a solution of ammonium nitrate. Enthalpy change= kJ/mol
Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
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