Nitroglycerin (C3H5N3O9), a liquid at room temperature (25 °C) and atmospheric pressure (1.01325 x 105 Pa), is used to relieve angina. It may undergo decomposition under these same conditions to form nitrogen, carbon dioxide, oxygen and water, with an enthalpy of decomposition of -1541 kJ mol-¹. The standard enthalpies of formation of water and carbon dioxide are -285.9 and -393.5 kJ mol-¹ respectively. (a) Calculate the work done when 1.0 moles of nitroglycerin decomposes and additionally explain the significance of the sign.
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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