Nitric oxide is produced industrially by the catalytic oxidation of ammonia:
4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(l)
Standard enthalpies of formation (kJ mol−1) at 298 K:
NH3(g): -46.1 NO(g): 90.3 H2O(l): -285.8 O2(g): 0
(a) Calculate the standard enthalpy change, ΔHrxn∘, for the oxidation of ammonia as written above.
(b) Determine whether the reaction is exothermic or endothermic, and justify your answer using the value from part (a).
(c) A reactor must release exactly 1.00×103kJ of heat to maintain its operating temperature. Calculate the mass of NH3(g) that must react to provide this amount of heat.
(d) If the reaction were carried out at twice the scale (i.e., twice as many moles of every reactant), predict how the ΔHrxn∘ per mole of NH3 would change, and explain your reasoning.