How much heat is absorbed during production of 112 g of NO by the combination of nitrogen and oxygen?

N2 (g) + O2 (g) →2NO (g), ΔH = + 43.0 kcal

From the given chemical equation we see that 43 kcal of energy is needed for every 2 moles of NO. First let us calculate the moles of NO with a molar mass of 30 g/mol.

moles NO = 112 g / (30 g/mol) = 3.73 mol

So the total heat absorbed is:

heat = (43 kcal / 2 mol) * 3.73 mol

heat = 80.195 kcal