Multiple Choice
Which statement about the standard enthalpy of formation (ΔH_f^ext{∘}) is true?
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8. Thermochemistry
Enthalpy of Formation
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Which of the following substances has a standard enthalpy of formation (ΔH_f^ext{∘}) defined as 0 kJ/mol?
A
Ne (g)
B
H_2O (s)
C
CO_2 (g)
D
F_2 (g)
Verified step by step guidance1
Understand that the standard enthalpy of formation, \(\Delta H_f^{\circ}\), is defined as the enthalpy change when one mole of a compound is formed from its elements in their standard states.
Recall that the standard enthalpy of formation for any element in its most stable form under standard conditions (1 atm, 25°C) is defined as 0 kJ/mol.
Identify the substances given: Ne (g), H_2O (s), CO_2 (g), and F_2 (g). Determine which are elements and which are compounds.
Recognize that Ne (g) is a noble gas element in its standard state, while H_2O (s), CO_2 (g), and F_2 (g) are either compounds or elements but not all in their standard elemental form.
Conclude that the substance with \(\Delta H_f^{\circ} = 0\) kJ/mol is the element in its standard state, which is Ne (g) in this list.
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