What is the enthalpy of formation for the substances, given the thermochemical reactions? Assign whether the process is endothermic or exothermic.

a.) Determine ΔH?_f for magnesium nitride.

3Mg (s) + 2NH₃ (g) → Mg₃N₂ (s) +3H₂ (g) ΔH? = -371 kJ

1/2 N₂ (g) + 3/2 H₂ (g) → NH₃ (g) ΔH? = -46 kJ

b.) Determine ΔH?_f for dinitrogen pentoxide.

2H₂ (g) + O₂ (g) → 2H₂O (l) ΔH? = -571.5 kJ

N₂O₅ (g) + H₂O (l) → 2HNO₃ (l) ΔH? = -76.6 kJ

1/2 N₂ (g) + 3/2 O₂ (g) +1/2 H₂ (g) → HNO₃ (l) ΔH? = -174 kJ

c.) Determine ΔH?_f for copper (II) oxide.

2Cu (s) + S (s) → Cu₂S (s) ΔH? = -79.5 kJ

S (s) + O₂ (g) → SO₂ (g) ΔH? = -297 kJ

Cu₂S (s) + 2O₂ (g) → 2CuO (s) + SO₂ (g) ΔH? = -527.5 kJ

d.) Determine ΔH?_f for magnesium nitrate.

8Mg (s) + Mg(NO₃)₂ → Mg₃N₂ (s) + 6MgO (s) ΔH? = 3884 kJ

Mg₃N₂ (s) → 3Mg (s) + N₂ (g) ΔH? = 463 kJ

2MgO (s) → 2Mg (s) + O₂ (g) ΔH? = 1203 kJ