Question

Calculate the enthalpy of the reaction 2NO(g)+O2(g)→2NO2(g) given the following reactions and enthalpies of formation: 12N2(g)+O2(g)→NO2(g),   ΔH∘A=33.2...

Calculate the enthalpy of the reaction 2NO(g)+O2(g)→2NO2(g)

given the following reactions and enthalpies of formation:

12N2(g)+O2(g)→NO2(g),   ΔH∘A=33.2 kJ

12N2(g)+12O2(g)→NO(g),  ΔH∘B=90.2 kJ

Homework Answers

Answer #1

2NO(g)+O2(g) → 2NO2(g) ; H = ?                   --------------------- (1)

Given reactions are

1/2N2(g)+O2(g) → NO2(g),   ΔHA =33.2 kJ            --------------------------(2)

1/2N2(g)+1/2O2(g) → NO(g),  ΔHB =90.2 kJ          -------------------------(3)

Eqn(1) can be obtained from Eqn(2) & Eqn(3) as follows :

Eqn(1) = [2x Eqn(1)] + [2xreverse of Eqn(2) ]

So H = (2x ΔHA ] + [2x(-ΔHB )]

             = (2x33.2 kJ ) + [2x(-90.2 kJ)]

            = -114.0 kJ

Therefore the enthalpy of the reaction is -114.0 kJ

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