According to strict IUPAC thermochemical conventions, which of the following elemental substances po — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

Standard states dictate $\Delta_f H^\circ = 0$ exclusively for pure elements residing in their most thermodynamically stable reference allotrope or phase. For Carbon, the stable reference is graphite (diamond is $ eq 0$). For Sulphur, it is rhombic (monoclinic is $ eq 0$). For Bromine, it is liquid $Br_2(l)$ (gaseous is $ eq 0$). For Phosphorus, highly reactive white phosphorus is the accepted reference (red is $ eq 0$).