# 11 Nitrogen oxides undergo many interesting reactions in the environment and i

Question

# 11


Nitrogen oxides undergo many interesting reactions in the environment and in industry. Given the following information, calculate H for the overall equation:
2 NO2(g) + 1/2 O2(g) N2O5(s).

2 NO(g) + 3/2 O2(g) N2O5(s), H = -223.7 kJ

NO(g) + 1/2 O2(g) NO2(g), H = -57.1 kJ

H = kJ Nitrogen oxides undergo many interesting reactions in the environment and in industry. Given the following information, calculate Delta H for the overall equation: 2 NO2(g) + 1 / 2 O2(g) rightarrow N2O5(s). 2 NO(g) + 3 / 2 O2(g) rightarrow N2O5(s), Delta H = -223.7 kJ NO(g) + 1 / 2 O2(g) rightarrow NO2(g), Delta H = -57.1 kJ

Explanation / Answer

(1) 2 NO(g) + 3/2 O2(g) -> N2O5(s), deltaH1 = -223.7 kJ

(2) NO2(g) -> NO(g) + 1/2 O2(g), deltaH2 = +57.1 kJ (reaction is reversed so delta H is positive)

Reaction (1) + 2 x Reaction (2) gives:

2 NO(g) + 3/2 O2(g) + 2 NO2(g) -> N2O5(s) + 2 NO(g) + O2(g)

Cancel common terms:

2 NO2(g) + 1/2 O2(g) -> N2O5(s)

Add up deltaH1 + 2 x deltaH2

deltaH (reaction) = -223.7 + 2 x 57.1 = -109.5 kJ

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