Calculate the Enthalpy Change at 298 $\Delta_{\mathrm{f}} H_{208}^{\circ}$ Data in Appendix 7:
2 Cl (G) → Cl₂ (G)

Calculate the enthalpy change at 298.15 K and 1 bar pressure for the following reaction, using $\Delta_{\mathrm{f}} H_{208}^{\circ}$ data in Appendix 7:
2 Cl (g) → Cl₂ (g)

A) - 121.7 kJ mol^-1.
B) 0 kJ mol^-1.
C) - 243.4 kJ mol^-1.
D) + 243.4 kJ mol^-1.