that water vapour, rather than liquid water, is formed in both reactions. b. Which is the more energetic fuel, per unit mass? c. Consider a fixed mass of each fuel. Which fuel would allow you to drive a greater distance? Explain briefly d. Describe how methane and hydrogen could be obtained. Which of these methods do you think is less expensive? Explain.
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.
Consider methane, CH₄, and hydrogen, H₂, as possible fuel sources
a. Write the chemical equation for the complete combustion of each fuel. Then find the enthalpy of combustion, △Hcomb, of each fuel. Express your answers in kJ/mol and kJ/g. Assume that water vapour, rather than liquid water, is formed in both reactions.
b. Which is the more energetic fuel, per unit mass?
c. Consider a fixed mass of each fuel. Which fuel would allow you to drive a greater distance? Explain briefly
d. Describe how methane and hydrogen could be obtained. Which of these methods do you think is less expensive? Explain.
e. Which fuel do you think is more environmentally friendly? Explain.
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