Question

Determine the enthalpy of reaction, ΔH° for the following reaction,

2 NO(g) + O2(g) → 2 NO2(g) ΔH° = ?
. the following data:
N2(g) + O2(g) → 2 NO(g) ΔH° = +183 kJ
½ N2(g) + O2(g) → NO2(g) ΔH° = +33 kJ
a. –333 kJ
b. –150 kJ
c. –117 kJ
d. +115 kJ
e. +238 k

Answer 1

To determine the enthalpy of the given reaction, you can use Hess's law. First, reverse the second equation and multiply it by 2 to cancel out NO₂:

2 NO₂(g) → N₂(g) + 2 O₂(g) ΔH° = -33 kJ

Now, add this reversed equation to the first equation:

2 NO(g) + O₂(g) → 2 NO₂(g) ΔH° = +183 kJ
+ (2 NO₂(g) → N₂(g) + 2 O₂(g) ΔH° = -33 kJ)

This results in the target reaction:

2 NO(g) + O₂(g) → 2 NO₂(g) ΔH° = 150 kJ

Therefore, the correct answer is (b) -150 kJ.