Physical State in a Thermochemical Equation
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State
A reaction's enthalpy change depends on the physical states of every reactant and product, so a thermochemical equation must show them.
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Forming liquid water from hydrogen and oxygen releases 286 kJ per mole, but forming water vapor from those elements releases only 242 kJ.
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Omitting a state label from a thermochemical equation leaves its ΔH value ambiguous between two different quantities.