Chemistry - Thermodynamics - I Question with Solution | TestHub

The term 'standard state' implies that the temperature is $0^{\circ }\mathrm{C}$

The standard state of pure gas is the pure gas at a pressure of 1 bar and temperature 273 K

${\Delta }_{\mathrm{f}}{\mathrm{H}}_{298}^{\theta }$ is zero for $\mathrm{O}(\mathrm{g})$

${\Delta }_{\mathrm{f}}{\mathrm{H}}_{500}^{\theta }$ is zero for ${\mathrm{O}}_2(\mathrm{g})$