For which one of the following reactions is ΔH°_rxn equal to the heat of formation of the product? A)N₂ (g)+ 3H₂ (g)→ 2NH₃ (g) B)(1/2)N₂ (g)+ O₂ (g)→ NO₂(g) C)6C (s)+ 6H (g)→ C₆H₆(l) D)P (g)+ 4H (g)+ Br (g)→ PH₄Br (l) E)12C (g)+ 11H₂(g)+ 11O (g)→ C₆H₂₂O₁₁ (g)

Question

Quizplus · Accepted Answer

The heat of formation ($\Delta H^\circ_{f}$) of a compound is defined as the change in enthalpy when one mole of the compound is formed from its elements in their standard states. Choice B represents the formation of $NO_2$ from its elements (nitrogen and oxygen) in their standard states (N$_2$ as a diatomic gas and O$_2$ as a diatomic gas), with the coefficients adjusted to produce exactly one mole of the product, $NO_2$. This directly matches the definition of the heat of formation.

For Which One of the Following Reactions Is ΔH°rxn Equal

For Which One of the Following Reactions Is ΔH°_rxn Equal