When 1 mole of methane burns, the energy released is used to heat water. This illustrates that
Correct answer: C. energy is transferred from the system to the surroundings but the total remains constant
- A. energy is created during combustion
- B. energy is destroyed during combustion
- C. energy is transferred from the system to the surroundings but the total remains constant
- D. the enthalpy of the system increases
Explanation
The chemical energy stored in the bonds of methane and oxygen is converted into heat, which passes to the water, so nothing is created or destroyed and the first law holds. The system loses enthalpy, which is why the value is negative, while the surroundings gain the same amount. Every combustion process is an example of this transfer.
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About First Law of Thermodynamics
The first law states that energy is conserved, so the change in a system's internal energy equals heat supplied plus work done on the system, ΔU = q + w. Questions use sign conventions, expansion and compression work, state functions versus path functions, and the relation between internal energy and enthalpy.
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