standard enthalpy of formation

Question

ΔH°f of elements in their most stable form at 298 K is:

RankGuru · Accepted Answer

1. **Definition**: The standard enthalpy of formation ($\Delta H^\circ_f$) is the change in enthalpy when 1 mole of a substance is formed from its constituent elements in their most stable states.
2. **Stable Forms**: For example, $O_2(g)$, $C(	ext{graphite})$, $H_2(g)$, $Fe(s)$, etc.
3. **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**.
4. **Temperature**: This definition holds at the specified standard temperature (usually $298$ K).

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More standard enthalpy of formation Practice Questions

The standard enthalpy of formation of an element in its most stable state at 298 K and 1 atm is: