Answer:
- 2Na(s)+Cl2(g)→2NaCl(s)
- Na(s)+1/2Cl2(l)→NaCl(s)
- C(s)+O2(g)→CO2(g)
Explanation:
Hello,
In this case, we shall remember that formation reactions are those involving the direct reaction of the elements forming the required compound. In such a way, for the given reactions:
2Na(s)+Cl2(g)→2NaCl(s)
Na(s)+1/2Cl2(l)→NaCl(s)
CaCO3(g)→CaO+CO2(g)
C(s)+O2(g)→CO2(g)
CO(g)+1/2O2(g)→CO2(g)
Just:
2Na(s)+Cl2(g)→2NaCl(s)
Na(s)+1/2Cl2(l)→NaCl(s)
C(s)+O2(g)→CO2(g)
Involve the elements composing the final products at the reactants. For that reason, the enthalpy of reaction (ΔH°rxn) result equal to the enthalpy of formation (ΔH°f) of the given product.
Regards.