The enthalpy of the elements at 1 atm: pressure and 298 K is arbitrary given the value of:
Correct answer: D. Zero
- A. 0.1
- B. 1.0
- C. 29.8
- D. Zero
Explanation
The correct answer is Zero. In thermodynamics, the standard enthalpy of formation for an element in its most stable form at 1 atm pressure and 298 K is defined as zero. This is a convention used to provide a reference point, as it simplifies the calculation of enthalpy changes for chemical reactions. The other options (0.1, 1.0, and 29.8) do not apply because they do not represent the standard reference state enthalpy.
This question appeared on the ETEA MDCAT 2012 paper, which you can sit online with every answer explained.
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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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