[megh44]

i would love to learn how. the question is this, construct an enthalpy diagram to show the formation of NO2(g) from its elements in one step
1/2N2(g) + O2(g) = NO2(g)  deltaH* = +33.8kj

do the same for the two step process
1) 1/2N2(g) + 1/2O2(g) = NO(g)   deltaH* = +90.37
2) NO(g) + 1/2 O2 = NO2(g)     deltaH* = ?

find the value of delta H* for the second step. (beware of the + deltaH*!!)

so what i'm thinking for the first part "construct an enthalpy diagram to show the formation of NO2(g)" is i take the charge of 1/2 N and O and add those together for one line on the diagram and NO2 will be the other line on the diagram and i take the difference between those two lines...

then for the two step i'm not sure if they want really at all...

[enahs]

I got to be honest, I have no clue what you said when you explained your thinking/idea.

http://www2.ucdsb.on.ca/tiss/stretton/CHEM2/enthal09.htm
http://www.hazelwood.k12.mo.us/~dfarley/APChemI/apch5/Howtodrawenthalpydiagram.doc