Which equation is a correctly written thermochemical equation?

C3H8 (g) + 5O2 (g)→3CO2 (g) + 4H2O (l) , ΔH= −2,220 kJ/mol

Fe (s) + O2 (g)→Fe2O3 (s) , ΔH= −3,926 kJ

NH4Cl→NH4 + + Cl−

2C8H18 + 25O2→16CO2 + 18H2O , ΔH= −5,471 kJ/mol

A & D

Step-by-step explanation:

1.

C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

this equation is correct and balanced since it obeys law of conservation of matter which states matter can't be created nor destroyed excepting nuclear reactions but can change from one form to another with release of energy as heat if required. And also definite proportion.

2.

Fe + O₂ → Fe₂O₃

This equation is balanced and doesnt obey laws governing conservation of matter

The correct equation is,

4Fe + 3O₂ → 2Fe₂O₃

3.

NH₄Cl ⇄ NH₄⁺ + Cl

This is a dissociation reaction merely to show the respective ions combined to form NH₄Cl and isn't a thermal reaction.

4.

2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O

This equation is also correct.