Ethanol (CH₃CH₂OH) is being used as a gasoline additiveor alternative in many parts of the world.(a) Use bond energies to find Hrxnfor the combustion ofgaseous ethanol. (Assume H₂O forms as a gas.)(b) In its standard state at 25°C, ethanol is a liquid. Its vapor-ization requires 40.5 kJ/mol. Correct the value from part(a) to find the heat of reaction for the combustion of liquid ethanol.(c) How does the value from part (b) compare with the value you calculate from standard heats of formation?(d) “Greener” methods produce ethanol from corn and other plant material, but the main industrial method involves hydrating ethylene from petroleum. Use Lewis structures and bond ener-gies to calculate ΔH°ᵣₓₙ for the formation of gaseous ethanol from ethylene gas with water vapor.
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.
Ethanol (CH₃CH₂OH) is being used as a gasoline additiveor alternative in many parts of the world.(a) Use bond energies to find Hrxnfor the combustion ofgaseous ethanol. (Assume H₂O forms as a gas.)(b) In its standard state at 25°C, ethanol is a liquid. Its vapor-ization requires 40.5 kJ/mol. Correct the value from part(a) to find the heat of reaction for the combustion of liquid ethanol.(c) How does the value from part (b) compare with the value you calculate from standard heats of formation?(d) “Greener” methods produce ethanol from corn and other plant material, but the main industrial method involves hydrating ethylene from petroleum. Use Lewis structures and bond ener-gies to calculate ΔH°ᵣₓₙ for the formation of gaseous ethanol from ethylene gas with water vapor.
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