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Chemistry · THERMODYNAMICS
हिन्दीConsider the following statements regarding standard enthalpy of formation (\( \Delta_f H^\ominus \)): (A) By convention, \( \Delta_f H^\ominus \) of an element in its reference state is taken as zero. (B) \( \Delta_f H^\ominus \) for \( \text{C}(\text{graphite}) \) is zero, while for \( \text{C}(\text{diamond}) \) it is non-zero. (C) \( \Delta_f H^\ominus \) of \( \text{Br}_2(g) \) is zero at 298 K and 1 bar. (D) The reference state of sulfur at 298 K and 1 bar is rhombic sulfur. Choose the correct answer from the options given below:
Correct answer · Option 4
(A), (B) and (D) only
Explanation
Statements (A), (B), and (D) are correct. Statement (C) is incorrect because bromine's standard reference state at 298 K is liquid \( \text{Br}_2(l) \) with \( \Delta_f H^\ominus = 0 \), whereas \( \text{Br}_2(g) \) has \( \Delta_f H^\ominus = +30.91\text{ kJ mol}^{-1} \).
