Question

What is the standard heat of reaction for the formation of NO2(g) from NO(g) and O2(g)? Write the balanced equation first.

Answer 1

- 113.10 kJ/mol.

Step-by-step explanation:

Firstly, we should write the balanced equation of NO₂ formation.

2NO + O₂ → 2NO₂.

We have the standard heat of formation (ΔH°f) of:

ΔH°f for NO = 90.4 kJ/mol.

ΔH°f for O₂ = 0.0 kJ/mol. (element)

ΔH°f for NO₂ = 33.85 kJ/mol.

∵ ΔH° for the reaction = ∑(ΔH°f)products - ∑(ΔH°f)reactants = [2(33.85 kJ/mol)] - [1(0.0 kJ/mol) + 2(90.4 kJ/mol)] = 67.7 kJ/mol - 180.8 kJ/mol = - 113.10 kJ/mol.