Consider the following thermochemical equations : 8Mg(s) + Mg(NO3)2(s) ? Mg3N2(s) + 6MgO(s) ?H°rxn = -3884 kJ Mg3N2(s) ? 3Mg(s) + N2(g) ?H°rxn = +463 kJ 2MgO(s) ? 2Mg(s) + O2(g) ?H°rxn = +1203 kJ Use the above equations to calculate the ?H°f (in kJ/mol) of solid Mg(NO3)2. A. -222 kJ/mol B. -188 kJ/mol C. +94 kJ/mol D. -94 kJ/mol E. +188 kJ/mol