Hot water heaters often use natural gas (methane) to generate heat. Methane and oxygen react to form carbon monoxide according to the overall equation: 2CH4(g)+3O2(g) = 2CO(g)+4H2O(g) The enthalpy of formation for each compound are as follows: CH4: - 74.6 O2: 0 CO: - 110.5 H2O: - 285.8 Part A: calculate the overall enthalpy change of the reaction. Part B: A typical water heater contains 40.0 gallons of water. After a long vacation, you come home and turn your water heater from "vacation mode" to hot. How many moles of methane must be combusted to heat the water in your water heater from 30.0°C to 48.0°C? The density of water is 3.79 kg/gal, the specific heat capacity of water is 4.182 J/g°C, and the water heater has a heat capacity of 850.0 J/g°C.
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.
Hot water heaters often use natural gas (methane) to generate heat. Methane and oxygen react to form carbon monoxide according to the overall equation:
2CH4(g)+3O2(g) = 2CO(g)+4H2O(g)
The enthalpy of formation for each compound are as follows:
CH4: - 74.6
O2: 0
CO: - 110.5
H2O: - 285.8
Part A: calculate the overall enthalpy change of the reaction.
Part B: A typical water heater contains 40.0 gallons of water. After a long vacation, you come home and turn your water heater from "vacation mode" to hot. How many moles of methane must be combusted to heat the water in your water heater from 30.0°C to 48.0°C?
The density of water is 3.79 kg/gal, the specific heat capacity of water is 4.182 J/g°C, and the water heater has a heat capacity of 850.0 J/g°C.
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