Answer:
In all listed reactions, ΔH°rxn does not correspond to the ΔH°f of the resulting product.
Explanation:
The standard enthalpy of formation (ΔH°f) signifies the enthalpy change that occurs when 1 mole of a product is created from its basic elements in their standard states.
1/2 O₂(g) + H₂O(g) ⟶ H₂O₂(g)
ΔH°rxn does not equal ΔH°f of the product, since H₂O(g) is a compound rather than an element.
Na⁺(g) + F⁻(g) ⟶ NaF(s)
ΔH°rxn is not the same as ΔH°f of the product because Na and F are not in their standard states (Na(s); F₂(g)).
K(g) + 1/2 Cl₂(g) ⟶ KCl(s)
ΔH°rxn is not equal to ΔH°f of the product due to K being outside its standard state (K(s)).
O₂(g) + 2 N₂(g) ⟶ 2 N₂O(g)
ΔH°rxn does not match ΔH°f of the product as 2 moles of N₂O are produced.
In none of the above cases does ΔHrxn match ΔHf of the product.
