The conversion of natural gas, which is mostly methane,into products that contain two or more carbon atoms, suchas ethane (C2H6), is a very important industrial chemicalprocess. In principle, methane can be converted into ethaneand hydrogen: 2 CH4(g)----->C2H6(g) + H2(g) In practice, this reaction is carried out in the presence ofoxygen: 2 CH4(g) + 12O2(g)---->C2H6(g) + H2O(g) (a) Calculate K for these reactionsat 25 °C and 500 °C. (b) Is the difference in ΔG° forthe two reactions due primarily to the enthalpy term (ΔH)or the entropy term 1-TΔS2? (c) Explain how the precedingreactions are an example of driving a nonspontaneousreaction, (d) The reaction of CH4 and O2 to form C2H6 and H2O must be carried out carefully to avoid a competingreaction. What is the most likely competing reaction?
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.
The conversion of natural gas, which is mostly methane,into products that contain two or more carbon atoms, suchas ethane (C2H6), is a very important industrial chemicalprocess. In principle, methane can be converted into ethaneand hydrogen:
2 CH4(g)----->C2H6(g) + H2(g)
In practice, this reaction is carried out in the presence ofoxygen:
2 CH4(g) + 12O2(g)---->C2H6(g) + H2O(g)
(a) Calculate K for these reactionsat 25 °C and 500 °C.
(b) Is the difference in ΔG° forthe two reactions due primarily to the enthalpy term (ΔH)or the entropy term 1-TΔS2?
(c) Explain how the precedingreactions are an example of driving a nonspontaneousreaction,
(d) The reaction of CH4 and O2 to form C2H6 and H2O must be carried out carefully to avoid a competingreaction. What is the most likely competing reaction?
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