For the reaction 2NO(g)+O2(g)→2NO2(g), which of the following algebraic expressions gives the standard enthalpy change ΔHrxn∘ in terms of standard enthalpies of formation ΔHf∘?
a) ΔH∘=[2ΔHf∘(NO)+ΔHf∘(O2)]−2ΔHf∘(NO2)
b) ΔH∘=ΔHf∘(NO2)−[ΔHf∘(NO)+ΔHf∘(O2)]
c) ΔH∘=2ΔHf∘(NO2)−[2ΔHf∘(NO)+ΔHf∘(O2)]
d) ΔH∘=2ΔHf∘(NO2)−[2ΔHf∘(NO)+2ΔHf∘(O2)]