Standard Enthalpy Of Formation
ΔH°f of elements in their most stable form at 298 K is:
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About This Question
- Subject
- chemistry
- Chapter
- chemical thermodynamics
- Topic
- standard enthalpy of formation
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
Zero
- Definition: The standard enthalpy of formation (ΔHf∘) is the change in enthalpy when 1 mole of a substance is formed from its constituent elements in their most stable states.
- Stable Forms: For example, O2(g), C(graphite), H2(g), Fe(s), etc.
- Reference Point: By convention and to ensure a consistent scale, the enthalpy of formation for any element in its reference state is defined as exactly zero.
- Temperature: This definition holds at the specified standard temperature (usually 298 K).
This easy difficulty chemistry question is from the chapter chemical thermodynamics, covering the topic of standard enthalpy of formation. It appeared in the 2025 exam.
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