How do you equate heat of reaction to heat of formation?

Write the balanced chemical reaction whose $\Delta {H}_{\text{rxn}} = \Delta {H}_{f}$

Jun 12, 2017

See below.

Explanation:

The heat of reaction Δ_text(r)H is the heat involved when a reaction takes place.

If the reaction involves the formation of a compound from its elements in the standard states, the heat of reaction is also called the heat of formation Δ_text(f)H of the compound.

As an example, for the reaction

$\text{2H"_2"(g)" + "O"_2"(g)" → 2"H"_2"O(l)", Δ_text(r)H = "-285.8 kJ· mol"^"-1}$

This reaction involves the formation of a compound from its elements, so the heat involved is also Δ_text(f)H.

For a reaction in which a compound is formed from its elements,

Δ_text(r)H = Δ_text(f)H