A mixture of gaseous reactants is put into a cylinder, where a chemical reaction turns them into gaseous products. The cylinder has a piston that moves in or out, as necessary, to keep a constant pressure on the mixture of 1 atm. The cylinder is also submerged in a large insulated water bath. (See sketch at right.) 1 atm pressure piston cylinder From previous experiments, this chemical reaction is known to absorb 156. kJ of energy. water ba The temperature of the water bath is monitored, and it is determiņed from this data that 372. kJ of heat flows out of the gases system during the reaction. exothermic Is the reaction exothermic or endothermic? endothermic up Does the temperature of the water bath go up or down? down neither in Does the piston move in or out? out neither O does work Does the gas mixture do work, or is work done on it? work is done on it neither
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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