A 10.0-g sample of ammonium nitrate, NH4NO3, is added to 100.0 mL of water (density = 1.00 g/mL) in a Styrofoam calorimeter. The initial temperature of water and calorimeter is 25.0 oC. When the solid completely dissolves, the final temperature of the solution is 18.4 oC. (a) Calculate heat lost by water and by the calorimeter. (Heat capacity of calorimeter is 15 J/oC and the specific heat of water is 4.184 J/g.oC)(b) What is the total amount of heat (in Joules) absorbed by the system (the dissolution of solid NH4NO3). (c) Write an equation for the dissolution of NH4NO3(s) and calculate its molar enthalpy of dissolution, Hdissol. expressed in 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.
A 10.0-g sample of ammonium nitrate, NH4NO3, is added to 100.0 mL of water (density = 1.00 g/mL) in a Styrofoam calorimeter. The initial temperature of water and calorimeter is 25.0 oC. When the solid completely dissolves, the final temperature of the solution is 18.4 oC. (a) Calculate heat lost by water and by the calorimeter. (Heat capacity of calorimeter is 15 J/oC and the specific heat of water is 4.184 J/g.oC)(b) What is the total amount of heat (in Joules) absorbed by the system (the dissolution of solid NH4NO3). (c) Write an equation for the dissolution of NH4NO3(s) and calculate its molar enthalpy of dissolution, Hdissol. expressed in kJ/mol.
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