All the enthalpy changes are________________?
Correct answer: C. May or may not be A or B
- A. Negative
- B. Positive
- C. May or may not be A or B
- D. none
Explanation
An enthalpy change is the heat change at constant pressure, so it may be positive for an endothermic process or negative for an exothermic process. Students may choose negative because many familiar combustion reactions are exothermic, but enthalpy changes are not always negative.
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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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