Ammonia reacts with oxygen to produce nitrogen and water?

- 1276.2 kJ.

Explanation:

ΔHrxn = ∑(n ΔHproducts) - ∑(n ΔHreactants)

∴ ΔHrxn = [(6 x ΔHf H₂O) + (2 x ΔHf N₂)] - [(4 x ΔHf NH₃) + (3 x ΔHf O₂)],

∴ ΔHrxn = [(6 x - 241.8 kJ/mol) + (2 x 0)] - [(4 x -45.9 kJ/mol) + (3 x 0)] = -1450.8 kJ/mol + 183.6 kJ/mol = - 1276.2 kJ.

c-14 is carbon-14, or radiocarbon.   it is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)