Question

Nitrogen and oxygen can react directly with one anotheer to produce nitrogen dioxide according to

N2(g) + 2O2(g) --> 2NO2(g)

The reaction may also be imagined to take place by first producing nitrogen oxide

N2(g) + O2(g) --> 2NO(g)

which then produces NO2

2NO(g) + O2(g) --> 2NO2(g)

The overall reaction is found by summing reactions and gives

N2(g) + 2O2(g) --> 2N2O(g)

How does the enthalpy change for the first reaction compare to that for the fourth reaction? Does this illustrate that enthalpy is a state function? Explain.

Answer 1

Calculate dH for each reaction of interest (or all of them) as
dHrxn = (n*dHf products) - (n*dHf reactants) then compare to answer the question. Yes it is a state function because the sum is equal to the individual parts and to be a state function it doesn't matter how we get there. It only matters about the initial and final states.

Answer 2

Calculate the enthaplychange for the following reaction.
NO(g)+1/2O2(g) =NO2(g)