Final answer:
The correct heat of formation reaction for sodium chloride is Na(s) + ½Cl₂(g) → NaCl(s), which releases 404 kJ of energy. It is exothermic because the compound NaCl is more stable than its separate elements. The balanced equation accurately reflects the stoichiometry for one mole of NaCl.
Step-by-step explanation:
The heat of formation reaction for sodium chloride (NaCl) can be represented as:
Na(s) + ½Cl₂(g) → NaCl(s)
This reaction is exothermic, meaning it releases energy in the form of heat. Specifically, the formation of one mole of sodium chloride from elemental sodium (Na) and chlorine gas (Cl₂) results in the release of 404 kJ of energy. This indicates that the sodium chloride compound is more stable than its individual elements, which is why energy is released when NaCl is formed.
The correct equation for the heat of formation reaction is option c) Na + 1/2 * Cl₂ → NaCl, because this represents one mole of NaCl being produced from its elements. It is important to recall that chlorine exists as a diatomic molecule (Cl₂) in its elemental form.