For which of the following substance(s), the standard enthalpy of formation is/are zero? — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

Standard enthalpy of formation is zero for elements in their most stable state at 298 K. (a) C(graphite) is the standard state of carbon. (b) $O_3$(g) is not the most stable state of oxygen ($O_2$ is). (c) $I_2$(g): standard state of iodine is solid. (d) $Br_2$(l) is the standard state of bromine.