calculate the standard heat of combustion of Nitric Oxide from the following data:

1/2 N₂ + 1/2 O₂ gives NO (g) deltaH=90.7 KJ

1/2 N₂ + O2 gives NO₂ deltaH=34.02 KJ

1/2 N₂ (g)+ 1/2 O₂ (g)$\to$ NO (g) $∆$H₁ = 90.7 kJ  -------(1)

1/2 N₂ (g) + O₂ (g)$\to$ NO_{2 (g)}   $∆$H₂ = 34.02 kJ  ------(2)
Subtracting (1) from (2):

NO (g) + 1/2 O₂ (g) $\to$NO₂ (g)  $∆$H = 34.02 - 90.7 = -56.68 kJ