What is the value of AG° for combustion of ethanol? C2HSOH(I) + 302(s) → 2002(g) + 3H20(1) You are combusting the ethanol in an engine to do work. You need to do 450,000 J of work and the engine produces work at 23% efficiency. How many kg of ethanol do yo need to combust to get the work done?
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.
C2H5OH = delta H = -278 KJ/mol, delta G = -175 KJ/mol, S = 161 J/K mol
3O2 = delta H = 0 KJ/mol, delta G = 0 KJ/mol, S = 205.152 J/K mol
2Co2 = delta H = -393.5 KJ/mol, delta G = -394 KJ/mol, S = 214 J/K mol
3H2O = delta H = -242 KJ/mol, delta G = -229 KJ/mol, S = 189 J/K mol
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