Which molar heat has a higher ΔH value?
Correct answer: C. Heat of sublimation
- A. Heat of fusion
- B. Heat of vapourization
- C. Heat of sublimation
- D. Heat of evaporation
Explanation
The heat of fusion is the enthalpy change required to melt one mole of a solid substance at its melting point The heat of vaporization is the enthalpy change required to vaporize one mole of a liquid substance at its boiling point Among these molar heats, the heat of sublimation generally has the highest delta H value because it involves the breaking of intermolecular forces between the molecules in the solid state, as well as the energy required to overcome the pressure of the surrounding atmosphere and allow the solid to enter the gas phase directly. The heat of sublimation is the enthalpy change required to convert one mole of a solid substance directly into a gas at its sublimation point. The heat of sublimation generally has a higher delta H (enthalpy change) value compared to the other molar heats. The heat of evaporation is the enthalpy change required to vaporize one mole of a liquid substance at any temperature below its boiling point.
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About Enthalpy
Enthalpy is the heat content of a system measured at constant pressure, and its change indicates whether a reaction or physical process is endothermic or exothermic. The topic covers state functions, enthalpy diagrams, standard enthalpy of formation, combustion and neutralisation, and the relationship between ΔH and internal energy change.
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