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 in their most stable reference phase. Graphite and rhombic sulphur are the accepted standards. For phosphorus, highly reactive white phosphorus ($P_{white}$) is the standard, meaning $P_{red} \neq 0$.