What is the enthalpy of formation for the substances given

Question

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