Determine the standard enthalpy of formation for NO given the following information about the formation of NO₂ under standard conditions, and $\Delta$ H ${ } _ { f } ^ { \circ } \mathrm { }$ (NO₂) = + 33.2 kJ/mol.
2NO(g) + O₂(g) $\rightarrow$ 2NO₂(g) $\Delta$ H_rxn = -114.2 kJ

Question

Determine the standard enthalpy of formation for NO given the following information about the formation of NO₂ under standard conditions, and

\Delta

H

{ } _ { f } ^ { \circ } \mathrm { }

(NO₂) = + 33.2 kJ/mol.
2NO(g) + O₂(g)

\rightarrow

2NO₂(g)

\Delta

H_rxn = -114.2 kJ

Quizplus · Accepted Answer

The reaction given is 2NO(g) + O2(g) → 2NO2(g) with ΔHrxn = -114.2 kJ. The enthalpy change for forming 2 moles of NO2 is 2 × 33.2 kJ/mol = 66.4 kJ. Using Hess's law: 2ΔHf(NO) + 0 = 66.4 kJ - 114.2 kJ, solving gives ΔHf(NO) = 90.3 kJ/mol.

Determine the Standard Enthalpy of Formation for NO Given the Following