7. If the standard enthalpies of formation of HBr(g) and Br2(g) are -36 and +31 kJ mol-¹ (at 298 K) respectively, what is ArH(298 K) for the following reaction? H₂(g) + Br₂(g) → 2HBr(g)
A. -67 kJ mol-1
B. +103 kJ mol-1
C. +67 kJ mol-1
D. -103 kJ mol-¹​